Using mean nicknames to demean your enemy is pass-aggro 101. When Tom Cruise got mad that Angelina Jolie snagged the lead role in the movie "Salt" (it was originally supposed to be a dude … played by Cruise), Pitt responded by calling Cruise "Mr. Strange." That ought to shut him up.
The bad blood between these two dates back to their "Interview With the Vampire" days.
“He bugged me … There came a point during filming when I started really resenting him. He’s North Pole, I’m South. He’s always coming at you with a handshake, where I may bump into you. There was this underlying competition that got in the way of any real conversation,” Pitt was quoted as saying. [Celebitchy]