Mario & Luigi: Partners In Time

The second game in the Mario & Luigi RPG series, released in 2005 for the Nintendo DS. The Japanese name is Mario and Luigi RPG 2x2.

The game changes a few game mechanics from the first one, and teams the brothers up with their time-travelling baby selves (who otherwise appeared in the Yoshi's Island games) using hilariously bad time travel "logic". Princess Peach travels to the past and is promptly kidnapped when the Mushroom Kingdom of the past is invaded by the alien Shroobs. Our Heroes go into the past to find her and have to collect the crystal shards that formed the Cobalt Star that was used to power the time machine in the first place while teaming up with their infant selves as well. Other than that, it's still pretty much the same game with witty dialogue and funny animations and some limited usage of the DS's features. The move-sets were altered to give each pair (bros and babies) unique items and moves, such as only the babies using hammers, and the Bros. moves in battle have been replaced by Bros. items instead.

Tropes appearing in this game:

 * Aliens Are Bastards: The Shroobs in general.
 * Alien Invasion: By the Shroobs against the Mushroom Kingdom.
 * And I Must Scream: The fate of some Toads early in the game.
 * Back From the Dead: Interestingly, Fawful returns in this game as a shopkeeper despite apparently dying in Superstar Saga.
 * Who said he was dead? He was just thrown out of Bowser's Castle... thousands of feet in the air...
 * Bad Boss:
 * Balloon Belly: Baby Mario can get like this by guzzling from a water source.
 * Bandit Mook: Dark Boos, who steal an item from the Bros should their attack connect. They flee the next turn after they steal an item.
 * Big Bad:  Princess Shroob.
 * Big Damn Heroes:
 * Buried Alive: Petey Piranha does this to himself in his battle with him, although he only does it up to his oversized head.
 * Climax Boss: The fight against Bowser and Baby Bowser.
 * Cognizant Limbs: The final boss has seven parts, though only three - - actually need to be destroyed.
 * Butt Monkey: Luigi, as usual.
 * Collection Sidequest: Finding the buried beans to trade for goodies at Fawful's Shop.
 * Continuity Nod: Prince Peasley from Mario & Luigi: Superstar Saga appears on a poster at the Shroom Shop. And Fawful runs a shop.
 * Also, when you meet Kamek, he mentions once trying to kidnap the Baby Mario Bros., and that it didn't end too well.
 * Darker and Edgier: Just compare this game to the first. You've seen the And I Must Scream trope in the list, above, right? It gets worse.
 * Disc One Final Dungeon: You go through the Shroob Mothership about ten hours into the game.
 * Easily-Thwarted Alien Invasion: The Shroobs..
 * Evil Counterpart: The Shroobs often act like this to the Toads, even having an enemy ingame known as the Shroobsworth.
 * Evil-Detecting Baby: When Princess Shroob arrives in the Mushroom Kingdom disguised as Princess Peach, Baby Peach is seemingly the only one to recognize her as she cries right in front of her.
 * Also, Baby Luigi. He cries when he sees the ghost of the Cobalt Star.
 * Evil Twin: Princess Shroob has a very strikingly similar outfit to Princess Peach.
 * Exotic Entree: When baby Bowser is choking on stolen cookies, he is offered milk from Kamek, who insists it's from an evil cow.
 * Exposition Fairy: Stuffwell the talking suitcase.
 * The Faceless: Princess Shroob's face is not actually seen up until the point you enter the Koopaseum.
 * Fission Mailed: You have to lose to the Shroobs in Hollijolli Village so that the Baby Mario Bros. can join you.
 * Foreshadowing: Plenty.
 * Fridge Logic: In Partners In Time, apparently Mario was content to let the Shroobs destroy the past world as long as Peach is safe. Also, why would the old Toadsworth not recognize the young Toadworth, since he himself should've been able to remember that, as he was like an adult then?
 * Intrepid Reporter: Kylie Koopa is always out for the next scoop.
 * Ironic Nursery Tune: Hollijolli Village's background music is based around a depressing-sounding version of Jingle Bells.
 * Large Ham: Bowser, as usual. Given a twist by his unintentional fall through a Time Hole, where he meets his younger self, Baby Bowser (who can only be described as a Small Ham).
 * Last Villain Stand: Princess Shroob.
 * Make My Monster Grow: The Shroobs do this to Yoob. One can only wonder how the subsequent Womb Level properly functioned prior to the size change.
 * Mineral MacGuffin: The Cobalt Star shards.
 * Mood Whiplash: For most of the game you are treated to a cheerful, upbeat soundtrack, and then you get to the final boss and the tone of the music becomes dramatic.
 * And really cool.
 * The destroyed Toad Town section of the game is immediately followed by the celestial peace of Star Hill.
 * inverse: when you first arrive in the past, the first area has a bouncy, lively rendition of the original Mario theme, but then you get to Holli Jolli village, in a similar state to Toad Town with an equally depressing track; a sad version of "Jingle Bells".
 * My Future Self and Me: The gameplay hook for this game has the adult and infant Mario Bros. teaming up inside and outside battle.
 * Having both generations of Bros. together in battle lets you use attacks and Bros. Items in new ways, such as double jumps and fireballs that can target air enemies.
 * Nice Job Breaking It, Hero:
 * Nonstandard Game Over: the only Game Over that can happen outside of battle.  If you fail, the   falls as the screen fades to black, while you get mocked by Princess Shroob's creepy laughter.
 * Noodle Incident: Used by the gate to the Star Shrine when it talks to Luigi.
 * Ocular Gushers: Baby Luigi, Baby Mario, Baby Peach and Luigi all do this frequently.
 * One-Winged Angel:.
 * Point of No Return: Used and subverted : The fight against  is the point of no return, but Stuffwell warns you about it. Even better, after you pass the PONR, he gives you the possibility to go back to before the fight, asking you every time you hit a save point.
 * Portal to the Past: They conveniently start appearing all over Peach's Castle after E. Gadd's Time Machine returns useless.
 * Post Climax Confrontation:
 * Which happens to be quite an anti-climax.
 * Punny Name: Prof. E. Gadd. Egad. Geddit?
 * Sunnycide, as well.
 * Sad Battle Music: The Final Boss music.
 * Sealed Evil in a Can: The holds.
 * Sole Entertainment Option: The arcade housed in a freakin' VOLCANO
 * Soundtrack Dissonance: The ending credits theme, which sounds downright sinister compared to what you'd expect from an ending theme in a video game.
 * Speaking Simlish: Everyone. The Bros' version sounds vaguely Italian, with a few recognizable words; the Shroobs are entirely tonal.
 * Sugar Apocalypse: What happens to Toad Town and Hollijolli Village. The latter is probably more unsettling, it happens right as Mario and Luigi are watching, and right during Christmas.
 * This Is Sparta: Fawful. I WILL! HAVE! FURY!
 * Time Travel: The plot is half this and half Alien Invasion.
 * Timey-Wimey Ball: It's probably best not to analyze this at all, as the time travel doesn't even try to make sense.
 * Considering the series made little sense, anyway.....
 * I thought they just traveled back and forth, between 2 different time periods, like Ocarina of Time?
 * There's a great timey-wimey scene that combines Meanwhile in the Future with Ripple-Effect-Proof Memory -- The Bros give younger Professor E. Gadd a Eureka Moment, and we cut to older Professor Gadd, who is having the idea at the same time, and is aware that it's because his memory is changing.
 * Underground Monkey: Many enemies are merely Shroob versions of standard Mario enemies. One good example is the Tanoomba, which gets a Shroob variant in the final dungeon.
 * Warmup Boss: Baby Bowser and Junior Shrooboid.
 * What Happened to the Mouse?:
 * Wingdinglish: How the Shroob language is presented.
 * Womb Level: Yoob's stomach.
 * Villainous Breakdown: Given what a short temper Princess Shroob has, it's not surprising that she eventually goes berserk following the destruction of her Shroob mothership...
 * Wingdinglish: How the Shroob language is presented.
 * Womb Level: Yoob's stomach.
 * Villainous Breakdown: Given what a short temper Princess Shroob has, it's not surprising that she eventually goes berserk following the destruction of her Shroob mothership...