Line from The Odd Couple: Oscar is complaining about living with Felix [Unger], and says "I go out in the kitchen in the morning, and on the table is a note that says "we're out of corn flakes, F.U."
There was the movie “Out to Sea”, with Walter Matthau.
“Where did you go to school?”
“Oh, it’s a little place called, ‘F.U.’!”