Ronaldo joined the Old Trafford club from Sporting Lisbon in 2003 and spent six years with the Premier League side.
During his time there, teammates including Rio Ferdinand, would wind him up.
Peter Crouch reveals in his new book: “Rio Ferdinand would tell us stories about how Cristiano Ronaldo would stand in front of the mirror naked, running his hand through his hair, and say, ‘Wow. I’m so beautiful!’.
“The other United players would try to wind him up [by saying] ‘Whatever, Leo Messi is a better player than you’.
“He would shrug his shoulders and smile again. ‘Ah yes. But Messi does not look like this…’”
Ronaldo joined Juventus this summer in a £89million move from Real Madrid.