To be honest, a definitive answer to this mystery is not available but scholars like Richard Ellmann have provided good guesses. Ellmann believes the "U.P.:up" on the malicious postcard means Mr. Breen, the receiver, ejaculates urine instead of sperm during sex.
"U p" in James Joyce's Ulysses refers to the "University College Dublin." It is a colloquial abbreviation commonly used by the character Stephen Dedalus to refer to the university where he studied.
Do u mean James Adam
Ulysses
Ulysses S. Grant Uncle Sam Uncle Tom Underdog Felix Unger Usher Uma Thurman Ursula Andress Uncle Buck Uncle Wiggily Alice Upside Down John Updike
· Ulysses Butterfly
Ulysses
Ulysses (as in Ulysses S. Grant) Uthridge (a bit of a stretch...)
Ulysses, Uma, Ursula
· Ulysses Butterfly
U Ulysses Butterfly V Vulture
John F. Kennedy and Ulysses S. Grant are the only two who meet this condition/
U for Ulysses
· Ulysses Butterfly · Underwing (a moth)