The phrase comes from an American television commercial for a breakfast cereal. The phrase comes from the cereal's mascot, a bird that went crazy for the taste of the cereal. Thus "Kookoo for Cocoa Puffs" became synonomous in American pop-culture for someone who was mentally unhinged.
A term used to define a person, situation or emotion that is particularly fucking crazy, insane, weird, etc.
"That butt naked bitch outside digging in the trash is kookoo bananas."
"The molly I took at the club last night had me feeling kookoo bananas!"
"My coworkers are all going kookoo bananas after 6pm rolls up but we don't get off till 7..."
Leia when Vader blew up her planet cuz he was being a total d-bag and trying to rape her with his softball trophies. It sucks dude cuz her fake parents were on that planet and Jack Black needs to be better than that
12 step recovery jargon referring to someone new who talks about how great life is, now that they'resober. Usually meaning that the person is out of touch with reality.
The new guy seems pretty happy for a dude who has no job, no money and no family. He must be on a pink cloud.