"What Gainax did next" is the best term I've heard. They figured they hadn't had enough nuttiness and imagery in their previous offerrings, so they made this.
Let's try and keep this spoiler free.
There's this ordinary boring town. A boy lives there. He passes the giant steam iron on his way to school every day. He has a friend - sometimes girlfriend who often doesn't attend school. They talk about what they want to do with their lives and the difficulty in getting the thoughts out of their heads.
Then a woman on a scooter smacks him upside the head with a petrol driven guitar and things become rather more abnormal rather quickly.
Featuring robots, angels, RockStars?, BaseBall?, PaintBall?, government agents with mobile eyebrows, and a lot of guitars...
The plot of FLCL is actually rather simple. The plot also, is not the point.
Six episode OAV and great with it. Every other minute is TwoMinutesOfCrack. Yes, that adds up to several minutes being several crack-minutes.