Leaked Experience

Many games adjust the level of a newly recruited character to match that of the lead character, in an attempt to make that character immediately useful. In other situations, it is the responsibility of the player to level them up, usually putting them in dangerous fights but protected by the stronger characters to level quickly. This strategy is known as “twinking”, "babysitting" or "piggybacking", and is frequently used in online games to get new characters to your level so you can play fairly together. Games which do not take this trope into consideration may end up with a player leveling his first character to the maximum level through Level Grinding, and then all subsequent characters will join up also at maximum level, saving a lot of time gaining experience for side characters.

Some games will give unused party members a fraction of the experience points gained in fights, but many will just force you to use those characters once in a while to make sure they don’t get too weak. Games allowing you to switch out characters at any times are appreciated for this reason.

The ability to switch members of your party in battle at any time may have been popularized by Final Fantasy X, although some games predate this usage. Breath of Fire had this in its first game, only to drop it for the next two.

This is a form of Gameplay and Story Segregation; but a highly acceptable one.

Used to fight the Can't Catch Up phenomenon. A good way to get the Magikarp Power. Compare Experience Booster.

Action Adventure

 * Avoided in Castlevania: Portrait of Ruin, the only game where you control a pair of characters together. Charlotte and Jonathan, in addition to sharing Life and Mana meters, level in tandem, whether both of them are there or not.
 * After plowing through 11 missions as Nero in Devil May Cry 4, you are given control of Dante, and with him, the exact same amount of Proud Souls Nero managed to accumulate, allowing you to immediatly unlock a bunch of Dante's abilities. This applies to level replays as well: if one manages to get some Proud Souls, the other will recieve the same amount.

MMORPGs

 * In City of Heroes, a lower-level character can "sidekick" (for heroes) or "lackey" (for villains) to a higher-level character, temporarily becoming the equivalent of one level lower than their mentor as long as they're within 200 yards of the latter. More directly, almost all experience earned by any character on a team will also be gained by each of the team's other members, as long as they're already roughly the same level.
 * Issue 13, takes this a step further with "level pacts" -- a sort of permanent sidekicking ability: two players become, essentially, a duo, and they are always getting experience. If one character is logged out for three months, during which the other character gains twenty levels, then the first character comes back to find they've gained twenty levels. However, not leveling together means that the duo earns half as much XP as a normal solo character, meaning this is not for powerlevelling.
 * Issue 16 takes it even further. One of the biggest features in it is "Super-SideKicking", which means that everyone on the team is Sidekicked to either the team leader or the mission holder.
 * At this point (August 2010), it might even be considered either an inversion or a distillation - if a higher-level player joins a lower-level group, they earn experience proportionate to their level—and retain some of their higher level skills (and almost all of their enhancements) to compensate for the power drop. If a lower-level player joins a higher-level group, though, they're likely to still be startlingly ineffective in comparison to the rest. The obvious solution, disregarding specially-crafted missions, is to join lower-level groups to... er... help new players.
 * You wouldn't expect this trope to show up in an MMORPG, but a new World of Warcraft recruitment deal lets you level up your lower level characters one level for every two levels your recruitee gains. Warcraft also has Relics, armor and weapons a new character can use that were acquired by your previous, more experienced characters, which are stronger than the equipment the new character can gain on his own.
 * Atlantica Online is weird in that regard. Being in a group with other players causes Leaked Experience over all fighters, but mercenaries not participating in the battle don't gain any, and all new mercenaries you hire, no matter what level you need to have to recruit them, start at level 1 (or Level 10 in some cases, but that requires you to find a wandering NPC of that class and recruit them for a lot of cash). This also perfectly illustrates why this trope is common, leveling up a new mercenary from scratch is painful as all hell.
 * Another variation of Leaked Experience comes with the guild/town system. If your guild controls a town, every resident that is persuaded to settle down in that town gives bonus experience for everyone in that guild.
 * Finally, there are ways to acquire Experience Books which any character can read to boost their experience.
 * You also get from being in a party with another player's group and to a lesser degree if they are not in the same battle as you are which led to a form of partying called LDP (long distance partying) which is partying with other players just for the sake of the leaked exp.
 * High level quests, however, are notably one of the best ways to level a new mercenary as the experienced gained from quest is fixed proportionate to the game phase. While this gives a decent some for high level mercenaries, this potentially gives enough experience to be able to level up many times (you can only level up once per experience gain instance)
 * Granado Espada / Sword of the New World lets you control Leaked Experience via "Experience Cards". While completing a quest in most MMOs gives you direct EXP gain, GE instead gives you consumable items which grant experience to whichever characters you feed them to. Yes, characters: this game lets you own up to 6 characters and deploy up to 3 of them in your active party. But your Lazy Backup do not accrue normal-style Leaked Experience, so at that point it's your decision whether to use the Cards to catch them up, or just keep power-leveling your main party.
 * Final Fantasy XI: XP in Vana'diel averts this; any level spread larger than two in a party severely lowers XP to the point of uselessness.
 * Eventually, a "Level Sync" feature was added, which temporarily reduced everyone's level to a designated party member's level, allowing a high-level character to XP grind alongside a level 10+.
 * Then Abyssea came out, which introduced XP alliances (7-18 players as opposed to the former standard of 6), and level 30+ characters coming to an alliance to "leech" XP became widespread, due to a different XP formula being used in Abyssea (the more monsters of a particular family you kill in a row, the more XP you will get from them, regardless of level; allowing a patient level 30 character to eventually rack up 500XP+ per kill after several hours). Instead of assisting with the fighting, "leeches" run the alliance (by directing others what to fight, and keeping the alliance full of replacements for members who have to leave), spend their Forbidden Keys to open treasure chests that drop from XP monsters so the high-levels don't have to, or simply sit in the alliance soaking up XP while others do all the work for it (trading off sessions is standard etiquette between friends; doing this without explicit permission is considered extremely rude and will get you booted from the alliance).
 * Some hail this as the best improvement to leveling up in the entire game, while others complain that it will be the end of the game as we know it and aren't afraid to say so on the official forums.

Real Time Strategy

 * Present to a small extent in the Dawn of War II campaign, with characters who don't fight earning less experience than if they had.

Role-Playing Game
"I believe using all these multipliers on a level 100 Blissey would be instant level 100 for 5 out of 6 EXP groups."
 * In Final Fantasy XIII, once crystal points become available, at the end of every battle every character, whether or not they were alive at the end of the battle, in the battle, or even introduced yet they received the same amount crystal points. This made it so characters like Snow, who is absent from play for 4 or 5 chapters, rejoin the team with a huge amount of crystal points.
 * The Knights of the Old Republic series, Neverwinter Nights 2, and Mass Effect were especially kind in this regard. All characters gained experience equally, regardless of how who you're playing. The player just has a backlog of skill points to use up when they switch a character. This also applies to newly recruited characters, who have all of the skill points they would have had if they'd been with you from the start.
 * Neverwinter Nights and its expansions used a variant of this trope. If you leave a party member behind and come back later they will still be at their old level, but talking to them gives you an option to let them "catch up".
 * This system may be a Bioware standard; it features in Sonic Chronicles as well, but the catch is characters don't actually level up until you put them in the party. This is due to the level-up system, where you distribute bonus stat and skill points each time a character's level increases.
 * Mass Effect itself has only one character level for the entire player squad, meaning any characters you decide to use later or haven't used while you gained levels merely need to have their talents chosen.
 * In some of these games, particularly Mass Effect, the other characters are implied to have been with you all along. They talk about events as though they were present at the time, even though they clearly were not - having your entire party around would really have helped in a lot of situations.
 * Dragon Age: Origins plays the modern incarnation of this trope straight. When the main character levels up, the companions will automatically catch up to one level below him or her the next time you go to camp, even if they've never actually been in the active party.
 * The Baldur's Gate series was more standard: characters would join at a level similar to yours, but would gain no experience if you removed them from the party and came back later.
 * To be precise, they join at a level similar to yours. There are several possible levels for every character, the highest one that is under your level is the one chosen.
 * In the Pokémon series, any Pokémon sent out into battle receives a share of Exp regardless of whether they participate further. Placing a low-level Pokemon on the front line and swapping it out for a stronger one is a known strategy, although it costs the player one turn to do so.
 * The first generation had an "Exp.All" item that split half the battle experience between all party pokémon—though the amount of text displayed for all six pokémon gaining experience at once easily became an annoyance. The second generation onwards replaced it with the more-effective "Exp.Share" item, which when equipped on a pokémon gives them (and only them) half the battle's experience.
 * With the advent of Double Battles, a specific strategy involves having a high-level Pokemon use Explosion while the low-level teammate uses Protect to evade all attacks—for any opponent that gets KO on that turn, the low-level teammate receives all the experience.
 * Traded Pokémon receive 50% more experience points than ones you caught yourself. In-game trades are matched to the same level as what you traded, allowing you to acquire Pokémon at lower levels than they would normally be found at in the wild. Trades between games are not level-matched, and the Global Trade Station attracts some complaints due to the sheer stupidity of some players' trade requests. (Because you know you wanna trade off your Level 100 Arceus for a random Level 1 Rattata....)
 * Made worse by the fact that many of the cases are actually people purposely asking for low level legendaries they can't actually get as a way of storing mons on the GTS.
 * However, all traded Pokémon get boosted experience anyway, regardless of what level you received them. You still have to switch them, but it makes things faster. There's also a Lucky Egg hold item that increases experience as well, but it's not much better than using the EXP Share.
 * Generation V changes the series's experience model so that the amount of experience gained in battle is related to the ratio between the user's and opponent's level (before, it was strictly the opponent's level); if you use a Lv.5 and Lv.10 Pokémon to knock out one opponent, the Lv.5 one will receive twice as much exp. as the Lv.10 one. Bonus experience if the enemy Mon belongs to a trainer, for holding the Lucky Egg, for being traded, for being traded from a different-language game, for Pass Powers...


 * In the DS Digimon World games, your party is composed of three frontline digimon and three support digimon that don't attack and can't be attacked unless switched to the frontline. However, after every battle the exp provided by the enemies is applied for everyone, even the support party. Due to the stat raising mechanics, you can convert an Agumon, leave it on the support line and let it become a maxed Black War Greymon even if it never actually attacks anyone. Weird, if you think about it for a moment.
 * In Chrono Trigger, all party members gain experience (even those which are not in your party, but rather waiting for you in the End of Time), but only "in play" characters get tech points; also, a given pair or trio of characters must fight a combat scene together at least once, after all the relevant individual Techs are unlocked, to use a new Combo Tech.
 * X-Men Legends did this, because the game would be flat-out impossible if they didn't; there are enough characters that it would suck the fun right out if you had to level them all individually, and there are many times when a certain character is needed over others.
 * The second game nearly fully averts this though. There are still leak, but only very little, result in inactive character being many levels behind. Guide Dang It for someone who didn't get characters that has might, levitate, bridge building.
 * Rogue Galaxy plays it straight, with inactive party members getting a sizable percentage of the XP the active party gets.
 * Valkyrie Profile does it both ways, depending on the difficulty level. On easy or normal, new party members are scaled to your level. On hard, everyone starts at level 1.
 * Except Freya, who starts at level 2. And whose stats mirror those of her Easy/Normal self. Because she's Freya.
 * Ironically, on Hard you can make people much stronger, due to skills. Funny how that works.
 * There's also the EXP Orb, which lets you pool Story Experience to redistribute however you want among the characters, which helps if some of them miss out on a big EXP boost that, say, a boss fight will bring about.
 * Septerra Core has perhaps the nicest possible iteration of this. Not only does everyone share experience equally, regardless of who is being used (mercifully, since only three people fight at a time, and one has to be Maya), but "everyone" also includes those whom you haven't recruited yet. In a sense, the entire party has one experience progression (though characters level at different rates).
 * For clarity, the total experience is a value that is tracked for the party. Every character has the exact same number of experience points no matter what. However, each character has a different amount of experience points needed to reach each level, so the characters are going to level at different rates despite having the exact same total number of experience points.
 * Avoided in Final Fantasy IX, where you actively have to use the characters in combat to level them up. This becomes extremely irritating when you get Freya, Steiner and Quina back in Disk 3, they can be almost ten levels behind Zidane, requiring you to spend some additional time training them. Similarly, players who never trained Quina got an especially nasty surprise in Disk 3, where they are required to use him/her as the only other character besides Zidane in a major boss fight, which means the fight will basically be one-on-one if you didn't raise Quina.
 * Use of this trope in Final Fantasy VI can actually turn into a Disk One Nuke. Spending a little bit of extra time as soon as you get control of Terra in the Narshe Mines will level her up a good bit. As you get the next 4 or 5 characters over the course of the next 45 minutes of game time, they will always be one level ahead of your main character, meaning if you level Terra up to 15, Locke will be 16, Edgar 17, etc.
 * A bigger Disc One Nuke that doesn't require active grinding is just have a "turbo"-type controller (which will repeatedly press a button) and you can put your party in a big loop during the river escape from the Returner's Hideout. You have Banon along, who has a free, full-party heal. Run through once so the memory pointer defaults to the right place, turn on the turbo, and walk away.
 * However, a bug prevents Celes from learning Muddle in most player's games. It just so happens that the conditions under which this happens (Celes rejoins your party between levels 32 and 39 due to Leaked Experience) are commonly met when Celes rejoins your party . Most players don't even know she naturally learns Muddle.
 * In Final Fantasy VII, characters out of the party get experience leak even if they're dead; dead in-party characters, however, get none.
 * Also done in the Tales (series), with a catch: "bonus" experience achieved due to using certain moves will not be carried over to your non-active party members, and their abilities' usage (which needs to be at a set amount in order to unlock stronger/different abilities) will obviously not be affected.
 * In Tales of Phantasia you start with a character, Chester, which will be lost for a long time afterwards. When you finally meet him again, you other team members will be way ahead of him and he is pretty useless. To make up for it, he gains Level at an incredible rate, making him level about two or three times as fast as the others. This way he can quite easily reach the highest ranks, while the others fall behind. And in remake versions, you'll occasionally get cutscenes in which he trains himself while everyone else is sleeping, catching his levels up to the rest of the party.
 * The remake also features an Optional Party Member, Suzu, that can gain a lot of experience to catch up to the rest of the party through an only mildly difficult "trial".
 * Tales of Symphonia plays this straight, but its sequel, Dawn of the New World, throws it all out the window. Characters from the previous game appear at a fixed level and do not gain experience. The monsters you capture, however, always start at level 1 (no matter how high level they were in the fight!) but level ridiculously quickly compared to human characters.. but then when they evolve, back to level 1. Though they retain a percentage of the stats they had in their last evolution, and evolution lines loop; so by continually leveling and evolving a critter, it became stronger and stronger and stronger.
 * Tales of Graces gives non-combatants 60% EXP from battles, and this can be increased with skills. This becomes unintentionally hilarious when it turns out the max bonus increase for every character (save one) is +50%. That's right: It's possible for characters not fighting to gain more EXP than the characters who are!
 * Kingdom Hearts also uses the "one experience progression" idea, since party adjustment is limited to swapping out either Donald or Goofy for a world-specific guest character. In Kingdom Hearts II,.
 * In the first game, the fastest way to reach the level cap was to fight Sephiroth over and over. Even though only Sora fought in the fight, Donald and Goofy leveled too.
 * Characters who are knocked out in combat don't gain experience in the first game. Oddly, this meant that on the hard difficulty, it was actually easier for a good portion of the game to level Glass Cannon Donald up by leaving him out of the party.
 * The .hack// games also use this, as characters you don't play with for a while gain levels to close to your new level. Justified as the other characters are people playing an MMORPG, and presumably, they still play the MMO when not in your party.
 * While most of the characters in EarthBound joined at reasonable levels, Paula joins the party at level 1 at a point in the game where the main character is likely level 15. The only assistance the player is given is the fact that Paula comes with a Teddy Bear, an item that serves as an attack target for enemies in battle, which might keep her from getting attacked long enough for her to gain a few levels.
 * The third character also starts at level 1, but you control him solo through his part of the journey, and, assuming you fight every enemy you encounter along the way, his level will be roughly equal to Ness and Paula's by the time he actually meets them.
 * The fourth character to join begins at level 1 as well, during a "Meanwhile..." sequence in which you control him solo during his zen final exam half a world away. The trope is given a halfway nod, though, when the spiritual breakthrough his exam is meant to confer manifests by pouring a load of experience into his empty coffers. He immediately jumps to just high enough of a level to obtain all of his primary psionic abilities (which are gained RPG-traditionally, no more than one per gained level), but still a good ten or twenty below the party's average at that point. This results in an unusual partial Leaked Experience effect, where a certain amount of the antithesis also occurs when the player jumps right into the next full-party battle and finds the new guy still sporting definite weak-link traits.
 * In Final Fantasy IV, the main character is reset to level 1 once he reconsiders some important life decisions. However, the main character is usually nearly as strong after the reset as he is before, even though he loses levels, and he gains his first few levels quickly. Once he's been through a few battles, it's actually a common strategy to solo him—almost everything in the area is weak to the element of his new sword after the level drop—both because it's easy levels and because of leaked experience. New party members have a set level, but ones that leave and return gain the same experience the main character does while out of the party, and at that point in the game there's only three characters who you've never had in your party (and one of those three doesn't benefit from gaining levels anyway), so almost everyone gains the XP from re-leveling the hero.
 * Unpleasantly averted in Lost Odyssey. Characters not in the active party receive no experience or any other character advancement in the form of Skill Points. Due to a heavy dose of Let's Split Up, Gang!, this can make certain parts of the game brutally difficult, if not almost impossible. Oddly enough, the game also tries to avoid Can't Catch Up syndrome; characters that are in use level up in very few fights, sometimes leveling up every single battle for a while up to an arbitrary maximum determined by the area you're in, at which point all experience gains quickly dwindle to near nothing. For characters who are level dependent on their skills, this allows fairly quick catching up. For other characters reliant on other ways to advance, it's still just down to Level Grinding.
 * Dragon Quest IV DS has both character swapping and leaked experience.
 * Dragon Quest IX averts this by distributing a bigger share of the experience to the highest level characters, a method inherently biased against classes that require more experience to level up.
 * In Dragon Quest Monsters: Joker, your active party gets full experience, and not only does your backup party gets a portion as leaked experience, but so does every monster you have in storage.
 * Played straight in Dragon Quest VII when one of your party members leaves . When she returns to the party later in the game she is still at the same level she was when she left while the rest of the party is a good 10-12 levels ahead of her by now. This is made especially annoying since you are almost immediately forced to fight the The Fire Elemental afterwards.
 * In the original Persona, characters rejoined the party after the prologue at the main character's level, making it much more efficient to concentrate on leveling him up before returning to the school and starting the game proper.
 * In the Shin Megami Tensei series, the skill Watchful (as well as its counterpart Growth in the Persona series) allows any demon/persona that have it to gain partial EXP even when not in battle.
 * Ignored, played with, averted, and then played completely straight through the Fallout series:
 * Companions in Fallout 1 don't level up, period.
 * Fallout 2 and Fallout Tactics simply apply the listed experience to each member of the party. There is no penalty to the player's earned XP for sharing it with others. Characters will only level up when in the player's active party, but the companions in Fallout 2 actually use a smaller, truncated level system than the player—each companion only has four or five "levels," and both a sound and some floating dialogue will indicate when a companion has leveled up. They don't get Perks like the player does, but gain bonuses to the SPECIAL (primary stats) instead.
 * Fallout Tactics averts this trope. While it applies XP like the previous title, all companions are fully customizable and do not level up from their spawn stats except by being active in the player's party.
 * Video Game/Fallout 3 and Fallout: New Vegas play this trope completely straight. A companion's level is directly tied to the player's, regardless of whether they've been best friends since level 5, are only just meeting at level 30, or haven't been seen for 10 levels. A few companions did not originally work this way, but have been patched to.
 * The exceptions being Fawkes, RL-3, and Dogmeat with the Fallout 3 add-on Broken Steel. The game classifies them as creatures instead of people, and some Good Bad Bugs moved the decimal point, making them ten times the player's level at all times.
 * Golden Sun: The Lost Age gives the lion's share to the active party, but the inactive characters still get half experience.
 * This format is continued in Golden Sun: Dark Dawn. Characters quickly catch up if they join at a lower level.
 * Digital Devil Saga partially uses this. Inactive characters automatically gain skill points, but not experience. This actually isn't too bad, as skill points are far more annoying to farm and there's a fairly easily unlocked skill that grants half XP when sidelined. New characters are also equal to the average level of the current party when they first join.
 * Final Fantasy XII handles this in two ways:
 * When characters first join your party they're generally around your level. This can lead to a Disc One Nuke if you level Vaan fairly high before anyone else joins.
 * Characters in "reserve" don't gain experience, but do gain points for the license board.
 * Averted in one character's case in Mega Man X Command Mission. When Steel Massimo joins your party (which would have been between Level 5-10 by now), he's at Level 1. Justified as
 * The same goes for Cinnamon, who also starts at Level 1, but has never fought a day in her life. Thankfully, she levels up quick hanging in reserve.
 * Averted completely in Star Ocean: Til the End of Time, to the point where characters can end up so far behind the main party they are more or less useless.
 * This is, of course, so you can send two (or three, if you recruited her) level 1 characters out against the final boss for a Bragging Rights Reward. It's very annoying otherwise, of course, since levels go up to 255.
 * Phantasy Star IV would leak experience to all characters that have been in, but since left, the party equal to the amount of experience each in-party character received. So if one in-party character dies, not only do the in-party characters get more experience, but the out of party characters get more experience as well. There is one point in the game were the main character, Chaz, temporarily goes through a short dungeon alone. This makes an excellent place to level up because not only does Chaz get a ton of experience from fighting alone, but each member of the rest of the party gets the same amount of XP from just standing around doing nothing at the dungeon entrance.
 * Eternal Sonata has unused party members gain a fraction of experience gained by active party members. Also, in the Mysterious Unison? Yeah, you'll probably be babysitting a lot if you want  to be useful.
 * Non-party characters in Legend of Dragoon gain experience in order to level up. What they don't get is the attack experience or spirit points needed to level up your Additions and Dragoon levels respectively.
 * In Fossil Fighters, you can carry five vivosaurs at a time, but only use three at a time in battle. All of them still gain experience regardless of whether they were used in the battle, which is very useful for levelling up weaker vivosaurs.
 * In Sonic Chronicles, experience is leaked to all party members, even those who haven't even joined your party yet, but it isn't given to them until you put them in your active party so that you can distribute bonus stats.
 * Super Mario RPG gives everyone experience for a battle, regardless of whether or not they participated or even survived. Truly a sign of a more entry-level RPG. However, your party members are always a set level and have a set number of experience points when they join. With some fine-tuning, you can set it up so that everyone has the same amount of experience points and levels up at the same time.
 * Agarest Senki 2 plays this trope straight. Party members who leave you (usually the non last generation protagonist and his love interests won't be at your level, but they can catch up pretty quickly anyway.
 * Same thing with Cross Edge.
 * All companions in Dragon Age II gain experience at the same time, even ones not currently in the party at the time. Some have lower initial exp when they join the party, but most of the time everyone will be at the same level.
 * Characters in Etrian Odyssey III: The Drowned City can learn the "Combat Study" Common Skill, which gives benched characters EXP from the main party's battles (to the tune of 1% per skill level, up to 10% at Lv10). You can also use your backup party to turn in completed Quests and Missions, netting them the reward without actually contributing to the effort.
 * Mount & Blade has a skill called Training, where experience is leaked to all lower-level characters at the end of each day. If enough people in the party possess this skill, one can raise a very competent army out of nothing in barely half a week.
 * In The Last Remnant, characters gain exp both for levels (which raises their stats) and the individual skills/arts they use. Team members (except for generic soldiers) that participate in a battle only gain exp for the arts they used in that battle, but benched party members gain exp in whatever arts that the main character Rush used in the battle. Thus, the fastest way to raise your team's skill levels is to have Rush fight battles on his own. However, this only affects the abilities they can use, and doesn't work for raising a character's stats.
 * Radiant Historia is weird about this. New characters join at reasonable levels. Characters in the party but not actually fighting get a sizable fraction of the experience. But characters that are out of the party entirely for plot reasons get nothing. So a character that joins the party and then gets seperated for a while ends up significantly below everyone else.
 * In Monster Girl Quest Paradox, characters in the reserve party receive just as much experience as those in the active party (the one that actually takes part in combat). One strategy for quickly leveling up low-level characters is to equip them with accessories and abilities that boost experience gain but come with downsides like reduced maximum HP, which don't matter for reserve characters as they're rarely exposed to danger.

Tabletop RPG

 * Dungeons & Dragons. In early editions, going up a level took double the Experience Points required to reach the previous level, and total experience gained was divided between all the party members. As a result, when a low level PC in a high level party survived an adventure they usually gained enough experience points to reach a level just beneath the rest of the PCs.
 * The 3rd-edition rules have a slightly different approach. Experience requirements go up exponentially, and a mixed-level party would gain different amounts—specifically, a lower-level character gets more XP for each encounter. Over the long run, this would close the level gap (or, at least, make it a lot smaller).

Turn-Based Strategy

 * In Fire Emblem, characters gain more experience if the enemy's level is higher than theirs. Therefore, a key strategy is to have stronger characters weaken, but not kill, an enemy, then let the weak character get the kill (and the lion's share of the experience). There is usually one character per game that has fantastic growth rates, but requires mucho babysitting to be a useful character.
 * Path of Radiance and Radiant Dawn have Bonus EXP that is awarded after battle for completing a map quickly, surviving NPCs and other stuff. You can award it to any of your characters how ever you see fit and even keep it for later.
 * It is worth noting, however, that in Radiant Dawn Bonus EXP is limited in its uses. Characters who use it to level up will gain exactly three stat increases per level, unless they've already maxed out so many stats that increasing three is impossible. Depending on how many stats the character in question has already capped, using bonus EXP can either be a huge boon or a handicap. Given that most low-level characters wind up much better if you level them the old fashioned way instead of Bonus EXP'ing them to a high level, this isn't a true replacement for babysitting. (None of this applies to Path of Radiance, where Bonus EXP is equally as effective as regular combat EXP.)
 * However, using this as Leaked Experience for your Laguz characters in Radiant Dawn is an excellent strategy. Because their stat caps are so low (Laguz stats double while transformed), feeding almost any Laguz character a healthy diet of Bonus XP is practically guaranteed to max all their stats. Laguz XP gains in combat are poor compared to Beorc, especially in the beginning, making this at least one case where the leaked experience is superior to the regular kind.
 * In La Pucelle: Tactics, a way to level up weak allies is to make a combo attack with a high-level character. If the said high-level character has a sufficiently high Speed stat, it will attack first, kill the enemy, and share the experience with as many as three adjacent allies, making it possible for a character to gain dozens of levels by observation.
 * The same goes for most other Nippon Ichi games, particularly stack-attacking in Disgaea 2, which let you split the experience ten ways.
 * One particular mission in Disgaea pits you against ten level 75 monsters in a Hopeless Boss Fight that ends in a Big Damn Heroes moment. The vassals that come to support you are all more than capable of defeating the monsters on their own, but with a bit of luck you can bring in a Warrior or Brawler to steal a killing blow and rack up about ten levels. Subsequent attempts at that mission replace the monsters with a single level 40 Fafnir, which is actually easily doable at that point and is good for power-leveling using combo attacks.
 * An even earlier mission covers the whole area in an invincibility Geo Effect save one square. In Disgaea you can throw monsters into each other, which stacks their levels. The monsters in that area can be combined into a single, level 117 monster. Repeat - there is one square in the whole map that does not have a permanent invincibility effect...
 * Absolutely critical in Battle for Wesnoth, which even advocates it in the hint system. While surviving any combat grants XP, the lion's share of XP goes to whoever lands the killing blow, so a typical strategy is to use high-level units to bring a powerful enemy to the brink of death and then have a low-level unit finally kill it.
 * Also, max level units gain little benefit from leveling up (most gain a minor health boost as opposed to new abilities), making it pretty pointless to give them killing blow XP.
 * Since healing doesn't give any XP and many healer units are almost worthless in combat, twinking healers is the only way to level them.
 * Final Fantasy Tactics A2 has new members always around the average level of the clan. Ironically, perfectionists aim to get them at a low level so that they have more control over their stat development. After they join, they only get exp if they participate actively in battle, but lower level characters tend to get much more exp.
 * Mostly correct, but random unit recruits cap at Level 30. Unique characters are not restricted by this.
 * This system is actually improved over the first game, where characters got exp based on the actions they did. A2 gives all characters an amount of EXP simply for being in the battle (with a penalty if they are overleveled), with extra EXP based on how much they actually contributed.
 * Likewise in Final Fantasy Tactics, characters not in a battle don't get XP, and new characters join at preset levels (Not to bad with most, but  and anyone hired from the soldier office will join at level 1 regardless of where you are in the game. And that secret characters joins at the very end. Leaked experience comes from Job Points (Used to learn new abilities), however. Whenever a character gains JP in battle, all characters in battle gain 25% of the JP themselves for that job. This can be rather useful for when you have a character first obtain a job that another character has been using for a while to find there's 1000 extra JP waiting for him.
 * Characters earn experience in Jeanne D'Arc with each action they execute during battle, as long as it hits. Afterwards, a hefty bonus is awarded to everyone in the roster, allowing the benchwarmers to catch up (albeit very very slowly.) Characters can even level up merely from this bonus, and it's not uncommon to have an active participant level up twice—once in battle, and again through the battle rewards. This also allows some of the benchwarmer characters to be used during parts of the game in which some characters who are universally "A team" characters are unavailable and the benchwarmers would be feasible substitutes
 * In Tactics Ogre and Knight of Lodis, each character actually has their own experience set, but the enemies that are often recruitable by Persuasion are set so that they are around the leader's level, and bosses are set so that they actually are a few levels higher than the leader in Knight of Lodis.
 * Better still - characters recruited by Persuasion are considered to have been in their current class for their entire careers, whereas your characters have to start in basic "Soldier" or "Amazon" classes which have lower stat growth. In the very long run, not a major issue, but right around the time when you're starting to convert your characters from the basic classes to the more complex ones, picking up a character who has five levels of the stat growth of a wizard versus training a newby to go through five levels of fighter first before becoming a wizard can make a significant difference.
 * In the PSP remake, class levels are separate from characters: IE the party has soldier levels, wizard levels, etc, that go up if you use that class in battle. If the party soldier level is 15, then any character you change to soldier and any soldier you recruit or persuade will be level 15, even if they were originally higher level. This has the annoying side effect when you get to recruit a character in the same battle that their class is unlocked for you: they join you, their class level resets to 1, and suddenly they can't wear the equipment they were just using in battle.
 * At the same time, characters have skill points which are earned like experience and are used to by skills and buffs. These skill points are not leaked at all, however, so a newly hired wizard (for example) will be woefully weak in comparison to the wizard you've had since the beginning: despite being the same level, the veteran will likely have buffs that significantly improve their stats.
 * Gladius gives the lion's share of XP to the team members who actually took part in a battle, but also awards a fraction of the XP to the others, meaning that even if you don't actively use a member they will be slowly gaining levels in the background, to ensure that you're not caught out in some of the more draconian entry requirements.

Fan Works

 * In The Games We Play by Ryuugi, a RWBY/The Gamer Crossover Fic, Jaune Arc's familiar Gou (a talking dog) gains experience when Jaune does, matching his level, even though Gou spends much of the story at Jaune's home, doing little or nothing. When he finally spends all the accumulated attribute points he's earned from his levels, the effect is profound.