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.
The track title "Chop U!" sounds either like an Unusual Euphemism or some sort of helicopter pilot institution. The track itself is awesome.
That One Boss — Envy, one of the Rivals that appear at the end of st. 5. Suffice to say that the usual guides for a 1CC explicitly instruct you to make Zenovia Airport the fourth stage, so you can structure things to fight Blunt and Sobut, but not Envy. That's how nasty it is. It mostly has to do with Envy's lasers being nightmarishly fast no matter how low the rank is.