Base-Breaking Character: Bowser has become this in hindsight, thanks to his more badass and competent appearances in Bowser's Inside Story, Dream Team and Paper Jam. Superstar Saga is arguably the Mario game that shows Bowser at his most patheticnote along with Mario Party 3, as he spends most of the game either as an amnesiac sidekick to Popple or a passive vessel for Cackletta, all while being kicked around by the universe and not having a single boss fight as himself other than the tutorial fight. As such, fans of Bowser's later appearances tend to dislike how he was portrayed in this game, while other fans find his comic relief antics amusing and enjoy his Butt Monkey role across the RPGs. Some in the latter camp argue that if Bowser wasn't benched in the story, then there wouldn't be as much focus on the other villains, and Superstar Saga was one of the very few Mario games at the time not to have Bowser as a main villain.
Clumphs. They got massive HP and generally come in pairs, making for a very long fight. And they're no slouches in the power department either, as they sport one of the biggest non-boss attack stats in the game. They can be instantly defeated by Mario's Fire Hand, but it's random and you got no experience by doing it. Even worse? They're Joke's End enemies, meaning you must battle them alone along with the other monsters in the zone. And if you're controlling Luigi (who lacks Fire Hand, meaning no instant defeat with him), prepare for a lot of pain.
The Gunner Guys in The Very Definitely Final Dungeon. They only have one attack, but it comes in two varieties and it's hard to determine how it will attack you. And if they hit you, you will not only take a lot of damage, but the risk of getting inmobilized too.
The same dungeon also features Hammer Bros (which generally appear along Gunner Guys, for extra fun. Hard to dodge attacks and very powerful makes them one of the most dangerous enemies in the game.
Popple will be taking this status, too, see? He even made a reappearance in Dream Team, albeit only for a bit part.
Game Breaker: The Mush Badge, which increases the Brothers' power depending on how many mushrooms they have. Go ahead and buy 99 of each mushroom. No one will stop you. This also makes Great Force more usable. Great Force doubles the damage you deal while also doubling the damage you take; that second part doesn't matter so much because, with both Great Force and the Mush Badge, you can destroy almost every boss in one round.
Get Great Force ASAP, which is after Chucklehuck Woods. Have one Brother equip that and have one equip the Bonus Ring, which you must have if you have Great Force. If you fight every enemy in the game after and take little damage, you can one hit kill almost any enemy in the game. Bosses can get taken down in two turns. With the Bonus Ring, which doubles Experience if you don't get hit, Great Force's side effect of the Bros. taking double damage starts meaning less, especially with bosses, where there are Save Albums right before... needless to say, a Great Force-Bonus Ring combo destroys anything, enough to the point where it's plausible to take out late-game bosses without Bros. attacks, including the final boss. Not as game breaking as the above example, but still makes the game pathetically easy.
The matching pants that complete the ensemble—the ones that boost your luck (chance to crit for extra damage) based on your Mushroom count.
Utilise Chopper Bros. extensively at level 3, and focus your level up bonuses on BP, ATK and SP, and you have a boss-killer attack, even if you don't use the advance version of the move.
Get the Advanced Thunder Bros. If you get it right, then it reduces the enemy's attack so that they only do 1 damage with each hit. And, it works on most bosses! It only hits one enemy, but since many of the bosses have only one section, that frequently doesn't matter.
The easiest way to max out all of your stats is to drink nothing but Teeheespressos. This is because Woo Beans and Hee Beans are the only two beans that are INFINITE and easy to collect, REGARDLESS of the fact that you can't specifically choose which stat you want to raise with Teeheespressos.
Troopeas, Elite Troopeas, Paratroopeas and Scaratroopeas. Why? Not only do they have very high defense, they can also heal or even resurrect other enemies in battle, including themselves, making them extremely annoying if you can't defeat them in one or two hits.
Magikoopas, for the very same reason as Troopeas (healing enemies and hard to kill), but with the extra feature that they can also boost other enemies or themselves, and attack with very powerful fire spells.
Malibuts. While they're not very strong, they retaliate as soon as you attack them, even if it's not their turn, and their attack have a fairly long animation, making countering them annoying and time-consuming.
Good Bad Bugs: Strength and Defense Buffs (and Debuffs) become permanent once you die. And they still stack with temporary buffs/debuffs.
Remember the entry about the Mushroom vs. Beanbean exchange rate? Now consider that Mario & Luigi: Dream Team ends with the Zeekeeper showering 80 million coins on Pi'illo Island, which would be used as a tourist attraction. Guess the big bird didn't really take inflation into account....
The penultimate battle against Fawful is a Shielded Core Boss. The final battle in Bowser's Inside Story is -also- a Shielded Core Boss, taken Up to Eleven. The Bros. have to attack the Dark Core above Dark Fawful's head, which they can't reach unless they take out his limbs, which they can't attack unless they take out his eyes. They can't even fight Dark Fawful at all until Bowser inhales him after making Dark Bowser spit him out.
Ho Yay: Luigi is flattered by Prince Peasley. Also Birdo toward Popple, depending on what gender Birdo you think is.
It gets worse. You end the game with the town in this state. Yeah, after having a nice town for a good portion of the game, it's reduced to this sorry state by Bowletta during the endgame.
The Oho Jees. In particular, the research team that was studying them accidentally lit one on fire. End result? It attacked one of the scientists, and the scientist transformed into an Oho Jee. Oh, and the research team regards it as no big loss, saying that science marches on.
Seinfeld Is Unfunny: Now that the main Super Mario Bros. platformers make a point of having Luigi playable and prominent, the jokes about his second-fiddle status and him staying behind to "protect the homefront" can lose some of the impact they originally had in 2003.
Trunkle can be a real pain depending on how you choose to fight him. The worst part about the mutant Sudowoodo thing is that there's no indication that you have to (let alone the fact that it's even possible) attack the orange in his hair instead of the beast itself.
Whichever friend of Jojora that you pick, it'll end up as this trope. If nothing else for taking too long. Especially if she uses her kissing attack to eat HP from your face or you try attacking her whenever Jojora is on the battlefield.
While Cackletta's Spirit isn't quite one, the beginning of the battle is. Both Mario and Luigi have only one hit point, and she gets to go first, unleashing a barrage of attacks that the player knows nothing about. And losing—that is, getting hit even once—means you have to fight Bowlettaall over again.
That One Level: Joke's End, in large part due to extended sequences where each Bro has to explore alone through enemy-filled territory and due to the labyrinthine design. Even the final dungeon is easier to navigate.
Walking along the Seabed can be a pain due to the slow movement speed and awkward swimming controls. Special mention must go to the sections where you have to swim over a bunch of spikes.
Teehee Valley is much shorter than Joke's End, but it compensates by sticking the player with a fairly annoying Escort Mission which ends with the battle against Trunkle, who is rather tricky unless you know what you're doing.
They Wasted a Perfectly Good Plot: The Beanstar ultimately plays no role in the story besides needing to be recovered and then reassembled, which is really a shame because this is a highly sought-after wish-granting trinket we're talking about here. Heck, you never even see it awake outside of its backstory and for a few seconds during the credits, which has led many to wonder what its personality was like (if it had one; it does seem sentient). This is especially glaring during the endgame: since Peach had been rescued by then, she could've woken it up so the Bros. could wish for a way to access Bowser's Castle in the sky, but they get there with Blablanadon instead.
What an Idiot: After Mario and Luigi put the Beanstar back together, they get a message from Bowletta, where they want Mario and Luigi to hand the Beanstar over to them at Joke's End in exchange for Princess Peach's freedom. After the message is done, Prince Peasly proposes to use a fake replica of the Beanstar to give to the baddies to trick them without giving up the real deal. Unfortunately, Fawful sees through the trick and knocks out Luigi when he shows the fake Beanstar, and steals the real one from him. The question here is, why bring the real Beanstar in the first place?