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.
YMMV: This Is The Only Level
All levels provide examples of:
Ear Worm: Polka, on repeat, used rather well, but so catchy.
Level 1 provides examples of:
Paranoia Fuel: The "Worried about nothing" stage. There are no traps, but you've come so far you're probably expecting there to be one.
Level 2 provides examples of:
That One Stage: "Corpse Shot". If you forgot about the panic button, that is.
Another contender is "Freefalling", which has the elephant freefalling while you try to guide it past the spikes to the goal. Let's just say that if you make it through this stage without feeling the urge to rip all hair out of your head, you are either an amazingly good player or a liar.
"AMAZEing" on FML mode.
Level 3 provides examples of:
That One Stage: "The Touhou Project". While nowhere near as bad as "Freefalling", the level is hard to beat if you're not in the right position to avoid the black dots.