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: Kirby and The Amazing Mirror
Awesome Music: The themes for Mustard Mountain, Radish Ruins, and Candy Constellation. Also, Dark Mind Form 2's theme.
Olive Ocean as well.
Goddamned Bats: The Bronto Burts. In addition to them, there's the Sword and Heavy Knights (they move fast), Leap (they'll kiss you if you're not careful in the air), and Roly-Poly (He rolls down slopes and bumps into you if you're not careful). Also the Batty enemy.
Phan Phan qualifies as That One Mid-boss. Between his pattern being randomized, moving insanely fast, and his attacks coming out quickly with little warning, he is by far the most annoying miniboss to fight.