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.
Crowning Music of Awesome: Pretty much the entire game, but the notable standouts include Stage 3 (Ken Ishii's "Creation (The State of Art)") and Stage 5 (Adam Freeland's "Fear (Don's Magical Adventure Mix)", which samples its main riff from Marlena Shaw's version of "California Soul").
Double Subverted with the Area 4 music ("ROCK IS SPONGE"). For most of the level, you get a cool, percussion-heavy piece. Then, out of nowhere, a random electric guitar appears in the boss. At first this seems jarring... but then you put the rest of the level out of your mind... and realize that the boss music is AWESOME.
Fridge Horror: Eden is shutting itself down because it's under so much stress from trying to handle so much information. You're tasked with...forcing it back into duty.