These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Big Lipped Alligator Moment: Upon clearing World 2 in Yoshi's Island DS, you're treated to a Cut Scene where Yoshi attempts to carry all three (at the time) babies at once. Unlike the other cinematics, this does not move the plot one inch.
Breather Boss: Quite common, with Salvo the Slime in the original, Cloud N Candy in Yoshi's Story and Gilbert the Gooey in Yoshi's Island DS. Funnily, two of the three mentioned examples are the first world's end boss, and usually come after a somewhat more difficult first boss in said world. Marching Milde, as mentioned in the Anticlimax Boss section, is also one of these.
Yoshi's New Island on 3DS is getting a bit of this for the graphics. Instead of reusing the "coloring book" look of the previous two games, the developers have chosen a style that resembles Yoshi's Island's artstlye mixed with Yoshi's Story pre-rendered 3D visuals, with backgrounds looking more painted and characters looking like claymation. Some love the style and think it fits in well with the usual Yoshi's Island aesthetic while still giving the game it's own identity, while others think it looks bland and lacks the charm of the previous games' coloring book style.
Not to the same extent, but some feel the name "Yoshi's New Island" is bland and unoriginal because Nintendo already used the "New" naming for their New Super Mario Bros. series of 2D platformers, and that Nintendo in general needs to stop adding the word "New" to games that act as revivals of older gameplay styles. Not helping is that it was confirmed that Nintendo once considered calling The Legend of Zelda: A Link Between Worlds "New Legend of Zelda" due to the game being a throwback to Zelda's early years.
The fact that Yoshi's New Island's opening cancels out the original's ending by including a twist that the parents who were brought the Mario Bros. are actually not their parents at all also has the fanbase split between the people who don't mind it & find it hilarious and the people who think that this is very disrespectful of the original Yoshi's Island's ending, which was considered a Crowning Moment of Heartwarming.
First Installment Wins: The original Yoshi's Island is still much more liked than Yoshi's Story and Yoshi's Island DS, so Yoshi's New Island had been presented like a successor to the original and reviewers all over are expressing disdain towards the new game.
Game Breaker: Collectible items like those Bullet Watermelons. It's very easy to use them to just blast spike pits to pieces, since the seeds can destroy thorns on contact and you get an absolute ton of them from just one melon.
Bandits can easily be these, as they run away with Baby Mario quickly and can jump onto small platforms through hordes of enemies with no problem. God forbid one gets caught behind some death spikes with the baby....
The literal bats found in cave levels. Especially in Yoshi's Island DS when the bats just keep re-spawning.
Good Bad Bugs: A programming oddity causes one of the introductions screens right when starting a level (that shows the level number and name) to stay on the screen longer than it usually does. Fittingly enough, it was The Very Loooooooong Cave. However, the GBA version fixed this, so it is only in the original version.
Many gameplay mechanics commonly assumed to have debuted in Super Mario 64 — such as the ground pound and red coins — actually first appeared in the SNES Yoshi's Island.
Yoshi's Island is also the first game to feature a certain remix of the Starman theme.
Player Tic: Touch fuzzy, get dizzy? You know you've done that deliberately.
The Scrappy: Poochy, as he's very difficult to control.
Scrappy Mechanic: The baby-switching in Yoshi's Island DS, especially because it's mandatory for most levels, and all babies but Baby Mario are Mighty Glaciers, which ruins speedruns. You also can't switch between levels, so you might end up with the worst baby for the next level, and you'll have to backtrack to switch to the preferred baby (and then you have to find a level that you can beat using it to keep it). Needless to say, it was axed for Yoshi's New Island.
So Okay, It's Average: To the people who don't dislike Yoshi's New Island, this seems to be a somewhat general consensus. A good amount of critics agree it's certainly *not* a "bad game," but because it's still seen as not living up to the SNES original it's generally regarded with opinions of "it's okay, but not great."
Surprise Difficulty: Particularly Yoshi's Island DS, but the original was no cakewalk either, especially if you were going for 100% in every level.
Visual Effects of Awesome: Thanks to the powerful Super FX 2 chipnote The Super FX 1 was famously used for the original Super NES Star Fox., many effects were employed here that were thought to be impossible on the SNES note including scaling and rotation with sprites, which could otherwise only be done with backgrounds (hence why some characters in the original Super Mario World were programmed as backgrounds)..