Always Check Behind the Chair

So, you've just made it through the latest ancient ruins or abandoned mansion, filled with rooms of oddly-present furniture at every turn. Along the way, you've killed monsters, triggered a Cutscene or two, and picked open every treasure chest you could find. You could call it finished and head back home—or, you could turn those seemingly empty bedrooms upside down in your search for more loot. (And whatever else is there.)

Always Check Behind the Chair is the process of examining inconspicuous objects, such as furniture or walls, in case the developers placed something there. When this trope is applied kindly, there will be some sort of general oddity or subtle deviation to show a secret's presence. Used in a more cruel manner, however, and it tends to dive into Fake Difficulty and/or Guide Dang It, especially when the item is plot-important or has literally no business being there. Such an example is placing the Infinity+1 Sword by a common bush.

What's behind the chair can be a number of things, but items, paths, monsters, switches and Easter Eggs are common. How they react to being discovered, however, is less concrete: switches may turn something on or off, but they're just as likely to unleash the Brutal Bonus Level's boss ramped Up to Eleven, start a mini-game, or provide some snark on particularly Willing Suspension of Disbelief-breaking events.

Some games feature a set of reusable locations for housing secrets, such as garbage cans and dressers, with the frequency of their placement capable of being a dead giveaway.

If the area becomes inaccessible after some point, the treasure may be Lost Forever.

Though primarily a Video Game trope, it can occur in other media, usually invoked by The Klutz or someone Genre Savvy.

The inverse of Notice This, where the game gives a clear, well-defined meaning to specific things to draw you in. Related to Pixel Hunt, which is the equivalent of this in point-and-click games. Often a case of Gotta Catch Them All.

Video Games

 * You can and should check trash cans for items in EarthBound. The fact that the protagonist picks up food items such as hamburgers and sandwiches from them has become something of a running gag among the game's fandom.
 * An Untitled Story: Very, very, very present. If you're aiming for 100% Completion, it's smart to check every corner big enough to hide a Heart Container.
 * Avalon Code. Every aspect of the game revolves around recording data into the Book of Prophecy, apparently to influence the 'new world' (as the current one is due to end). Whether it's simply exploring 100% of a map for completion's sake, or scanning that flower which gives you the code to upgrade your sword, this isn't a optional extra so much as a necessity for survival. Particularly as you can never tell which map/item will net you a crucial bonus, and some are really obscure (Rocks, grass, the ground, etc...)
 * A Vampyre Story: You have to check under your bed for an item in order to proceed. No one prompts you.
 * Fortunately, the developers decided to include a command (the tab key, specifically) to make a mark appear over everything you could examine. A couple puzzles, including the one mentioned here, appear to have been designed with the expectation that you're going to use this.
 * Barkley, Shut Up and Jam: Gaiden has this throughout the game, and it's specifically lampshaded with the trash bins in the Spalding Building.
 * "Found 0 nothings!"
 * Blue Dragon: Not only do some objects contain items you can take, but many more hold “Nothing,” which is apparently not the same as actually having nothing inside. Finding enough Nothings will let you get items from a certain NPC, including unique items not available anywhere else. The “Six Treasures” Downloadable Content includes a pair of glasses that places markers on top of things that are hiding Nothing.
 * Breath of Fire series: Chests or drawers, on more than one occasion. The first two installments also had some treasure hidden in statues and pillars, under pushable objects, and even some random sections of wall, propelling this right into Guide Dang It territory.
 * In the first installment you get several Infinity Plus One Swords this way. The Life Armor? In a dragon statue at the top floor of Agua. Don't forget the Ice Dagger in the other statue. The Tri-Rang? Search behind Pagoda either before it is activated or after it is ruined. The Empire Sword? Search the left side of Jade's throne. Oh, and check for the Star Hammer behind the right pillar in the same room while you're at it. If you know where to look, some of these become Disk One Nukes.
 * Chrono Cross has this all over the place.
 * Chrono Trigger has tabs, inconspicuous objects hidden throughout the landscape that occasionally glint to announce their presence. Other secrets are usually obvious.
 * Dark Souls has useful things behind containers, furniture, walls, and even illusory walls. In fact, two entire areas and a Covenant are hidden behind an illusory wall, behind a chest, behind another illusory wall.
 * Dead Rising and its sequel tend to love to hide useful, rare weapons in just-out-of-sight areas, like the roof of a magazine stand in the center of a mall, or a katana on the awning of a bookstore.
 * The Dragon Quest series has hidden items in barrels, pots, hanging bags, drawers, coffins, crosses, just lying on the floor... Most of the games after Dragon Quest III let you potentially learn a spell that lets you sniff out how many treasures are hidden in an area (while another reveals their whereabouts with a telltale sparkle).
 * More directly, the first and third games feature a hint on how to avoid an endless hallway: you must search behind the throne in the final dungeon, or you'll never reach the endgame. Making it this trope quite literally.
 * Disgaea: There are three locations inside the Overlord's Castle that must be examined to unlock Etna's diary—two switches and a corner. One switch is hidden behind the Overlord's throne; another is the skull on the RosenQueen shops' counter; finally, there's the corner of the pit in the room with the music merchant. In DS, the corner is made somewhat more obvious by a Prinny who comments that he “feels a breeze, dood.”
 * In the Doom games and their many, many custom levels, hidden switches frequently lead to secret areas and goodies. A favorite location for such switches is on the easily overlooked backs of chairs, columns, freestanding switch panels, etc.
 * The Elder Scrolls III: Morrowind loved this trope. Easily the best gauntlets in the whole game were only attainable by searching behind a few giant coffins. They were easy to miss if you weren't a compulsive klepto, as there's nothing of note by the coffins themselves.
 * A trend continued to some extent by the later sequel, The Elder Scrolls V: Skyrim - but not as much with items, as with where to find that lever to open a dungeon gate, or the symbols to solve a typical puzzle. In at least one case, the lever to open a door is LITERALLY 'behind the chair'.
 * As well, player mods for pretty much all of the moddable Elder Scrolls games play this as maddeningly straight as possible in many, many cases - such as one that puts a gold retexture of the Ebony Armor on a follower you can legally slaughter right outside the first town you get to after the tutorial. And what is said follower doing there? Camping. Ten feet from the town gate. For the entire game, if you never do pick him up.
 * Fallout 3 can become this if you're low on health items, ammo, guns or certain quest items. Not helped by almost every item that isn't nailed down being potentially collectable, and getting in the way of an item you actually want to pick up.
 * Bathrooms often also hide valuable loot (often chems) in the bowl or water tank of toilets. This means that each time you find a bathroom, you throw open each stall, run in and jump onto the toilet seat to get a better look. Each time.
 * Final Fantasy III dances between Always Check Behind the Chair and Notice This: the DS remake lets you zoom-in using L/R, with spots hiding objects giving off a yellow-gold sparkle.
 * Final Fantasy IV: Many areas have hidden goods or passageways, but Eblan Castle deserves special mention due to the sheer prevalence of such things. In summary: secret corridors on basically every floor; a Sutra hidden behind the throne; a pit that you have to edge your way across to reach a chest; and then, just to confuse you, a different and uncrossable pit. That's before The Very Definitely Final Dungeon's obsession with paths under paths under paths, all obscured by the top-view.
 * Final Fantasy VI: There are Elixirs in almost every grandfather clock.
 * Clocks are/were believed by alchemists to be optimum storage places for immortality potions.
 * The Godfather: Missions in the Wii version (and possibly others) have money bags hidden with varying degrees of visibility. If you don't get them while you can, they're Lost Forever.
 * Golden Sun did this, as well as its sequel. The items were mostly small, HP healing items or a few coins. But occasionally you lucked into a Lucky Medal, a rare item used to win other rare items later on. For the first half of the game you just have to stumble through and hope, but at a certain point you learn a skill that lets you examine an area. Pots, etc., with items in them sparkle. You still have no way of knowing what it is, and it takes forever if you want to check every pot, but it's better than nothing.
 * Harvest Moon: Animal Parade: you can often find recipes around people's kitchens, if you're willing to walk around pressing the A button for a bout two minutes.
 * Jed: Several robots are hidden past where the world seems to end, usually separated by a concealed passage or a low roof that can be walked on. Some of these are hinted at by inexplicable empty blocks inside the wall.
 * King's Quest IV: There's an island where you have to check behind a ship's detached front, which is lying in the sand. Rearward of the wreckage is a golden bridle that: 1) has no business being there; 2) is completely necessary to win the game. The island is only accessible at one point during play, and after leaving, you can't go back. Oh, and using “look” on the shipwreck only works when you're standing in exactly the right spot.
 * It is wise to do this in any Lego Adaptation Game if you want to get True Adventurer status, minikit pieces or red power bricks, although it's not so much checking behind the chair as it is destroying it with your fists.
 * Luigi's Mansion: Played straight. In several rooms, including the Study, there are hidden lumps of cheese behind or under chairs. Examining them will cause a golden mouse to appear, and catching it will reward the player with lots of treasure. If the room is cleared and the Mansion blackout has already occurred, you will never be able to get the treasures again.
 * Lust Grimm: If you want to avoid missing anything, you'll need to inspect crates, barrels, cupboards, trees, stumps of trees, bushes, empty patches of dirt...
 * Mega Man Battle Network: multiple ports and chips are hidden in the over-world.
 * Most of the bosses throughout the series can only be rematched for a chance to get their battle chip by walking to a specific, unmarked part of an area (Usually a dead end) which will initiate a battle against them.
 * Mega Man Star Force mostly follows in the footsteps of Network in its application of this trope.
 * The Metal Slug series will often hide items and hostages in the damndest places. Often places you wouldn't know there was anything there unless you shot it (like in the smoke coming from a Train's smokestack) or read a FAQ.
 * Pokémon: Standards of the series are patches of grass with a darker shade than others, inexplicable patches of no grass in the middle of a grassy area, trash cans, the centers of plateaus, dead-ends, and rocks; later games also add little hills of sand/dirt (although these can also be hidden trainers). Thank Arceus for the Item Finder when they're anywhere else.
 * And in the third generation games, accessing the Trick House challenges requires you to find where the Trick Master is hiding in a room.His position is made obvious by a glint just as you enter the house.
 * Seiklus: Though there's usually an eye-like marker along walls with hidden goodies, the haunted crypt notably doesn't for a couple places.
 * Shadow Complex does this a lot. Some expansions are hidden behind crates. Failing that, they are hidden just out of sight of the camera angle.
 * The Shadow Hearts series is very guilty of this. On the plus side, you'll get a little ? over your head when there's an item hidden nearby. If it's important to the plot, you get a !.
 * And if you find, you see a <3
 * The Shining Force series suffers from this on occasion. In the Japanese version of the first, Optional Party Member Hanzo was hiding in a shrub in the last town (the US version had a note on the correct one), while the second game had Mithril.
 * In Sonic Adventure on the SEGA Dreamcast and Sonic Adventure: DX, the remake for the Gamecube, when your on the Egg Carrier, in order to change the position of the wings you must first sit on Eggman's chair in the control room so that it moves forward, and then press the button which was hidden under the chair.
 * Suikoden II has some items hidden in patches of grass, bonsai, and random crates.
 * In Suikoden IV, one of the recruitable characters is behind a chair, and thanks to the camera angle when you enter the room, you won't realize it until you actually go behind said chair.
 * Super Metroid: until you find the X-Ray Scope, at least.
 * Tales of Symphonia has some treasure chests completely hidden behind furniture or terrain features, particularly in the final dungeon; there's nothing plot-relevant about any of them, but they're necessary for 100% Completion. Fortunately, the "examine" command still pops up when you stand next to one.
 * The Thief series was all about this. Finding every last piece of valuable loot in each level involved thoroughly checking every nook and cranny, and that's when there were no weird secret passages involved. The very first level of Thief 2 for example included 3 gold coins left on a shelf that could only be seen by looking up while going down the back stairs to the mansion's kitchen (or turning around midway while climbing up the stairs).
 * Snailiad, being a Metroidvania, obviously has this to some extent.

Web Comics

 * At the beginning of Darths and Droids, Jim and Ben's very first act of going Off the Rails involved searching a room for items rather than waiting for the negotiators to arrive. As punishment, the GM retroactively decided that this action was responsible for the Trade Federation attacking them.

Role Playing Games

 * The Munchkin's Guide to Power Gaming notes, in explicit detail, that the munchkin method of searching a dungeon does not only restrict itself to looking behind chairs, but actually breaking apart the chair to search for loot and/or magical items inside. As well as destroying all other furniture, breaking open the floor, walls and ceiling, as well as searching each monster corpse to the point of running their corpse through a sieve. After looting potentially valuable organs, of course.