Billy Crystal and John Goodman’s song from “Monsters’ Inc.”, “If I Didn’t Have You”, is closed with the word:
A-E-I-O That means you Yeah!
What does A-E-I-O mean? Why does it mean “you”?
AEIOU is the order of the English vowels and is something commonly learned/recited by schoolchildren. The song is just making a little joke on the fact that "you" sounds like the letter "U".