Christina Aguilera Curses Out Mickey Mouse

Powerhouse singer Christina Aguilera curses out Mickey Mouse at Disney California Adventure.

Christina Aguilera is not in the Christmas spirit ... she spent her birthday in "The Happiest Place On Earth" ... in a heated argument with Mickey Mouse ... TMZ has learned.

Our theme park source tells us while ringing in her 34th b-day at Disney California Adventure, Christina and her crew tried to get a pic with Mickey, but he was going on a break ... so Christina was told she had to wait. Cue meltdown!

Aguilera lost it, and called Mickey an "a**hole." We're told she even dropped the dreaded, "Do you know who I am?"

Xtina's crew started hurling threats, we're told ... and Mickey had to be ushered to a safe zone -- out of public view. Security was called, but by the time they arrived ... the former Mouseketeer had already split.

Jacked from TMZ