Keiichi Maebara's super hero state in which a super deformed version of himself flies around naked. The theme song is surprisingly catchy and annoying... but it's still hilarious.
This is a joke originating from Nyodude's Higurashi Parody Fandub.
Keiichi: "This looks like a job for... Keiichi's Chibi Angel Bottom!"
Keiichi: *singing to the tune of TMNT
* "Keiichi's Chibi Angel Bottom, Keiichi's Chibi Angel Bottom, Keiichi's Chibi Angel Bottom, heroes in an ass crack, chibi power!"
Shion: *punches Keiichi* "This is why I go crazy and kill people...!"