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.
Love It or Hate It: This is the general feel you get from the pizza trolls, once there's more than one of them.
Memetic Mutation: "FLEENS? You're not Fleens! Whatever you are... MAKE ME A PIZZA!"
The narrator's hammy line "Hip hip, ZOOMBIIIIIINIIIIIII! Hip hip, ZOOMBIIIIIINIIIIIII!"
Nightmare Fuel: Much of the game, due to the eerie music and often surreal visuals, but especially the final leg through the mountain caves, and especially Bubblewonder Abyss, which has a dark atmosphere, creepy sound effects in the background, and the ability to vaporize any Zoombinis who take the wrong path through the maze (sure, you get them back, but that didn't make it any less scary!).
That One Level: Pretty much everything on Very, Very Hard. Hotel Dimensia and The Lion's Lair deserve special mention. The hotel has literally 125 rooms, meaning it's Trial-and-Error Gameplay here more than ever. And there's no clock to gauge how many chances you have left. If you can't figure out where each one goes in the time allotted, then too bad. As for The Lion's Lair... in this level, you'd get some sort of hint as to how to properly order the Zoombinis. Your hint here? You don't get one. This basically makes it like Hotel Dimensia with less chances to screw up; after your sixth wrong placement, the gate slams down and you can't take anybody else through.