loony tune
English edit
Etymology edit
Probably after Looney Tunes cartoon characters, because these characters are noted for their silliness.
Noun edit
loony tune (plural loony tunes)
- (slang, humorous) A silly or crazy person; a person whose actions are unpredictable and irrational.
- Some loony tune parked his car in the no parking section.
- Stop fooling around like a loony tune and get to work on your essay!