Premise: This show isn’t actually summarized easily, so here are some elements in the show: robots, guitars, a psychotic pink haired girl, a boy whose head makes monsters, a yellow Vespa, awkwardness, and absurdity. Like, anime back then was even less bad, but this was like a bad anime that doesn't need any respect because it's garbage from king garbage of the garbage dynasty.
Genre: This anime is designed to mess with you, not by creating assumptions about who people are and then shattering them, but by simply discarding all semblances of normality. Just go with it. Like they did this better in Gundam.
Characters: There is something distinctly memorable about each of the main characters, but not in the simple “Haruko is a pink-haired girl who moves into Naota’s room” way. If you watch FLCL, you will remember the people, but probably not for the same reasons I do. I hate Haruka so much because he or she is a self-insert anime character of the week.
Title: What is Fooly Cooly? Watch the show and you still might not know. It appears to be a sexual act, but it’s never explicitly stated.
Story: There is one, because you must start at episode 1 for anything to make sense. I have been told that watching FLCL multiple times helps and that there are religious and ethical symbols.
Overall: Watch episode 1 and you’ll know if you want to continue. I can’t describe all that is Fooly Cooly for you. It's so bad that it was revivid years later and still sucks.
