'The Hangover Part II' Premiere Re-unites The Wolf Pack, and Then Some!

Bradley Cooper, Ed Helms, Zach Galifianakis, and Ken Jeong have all returned for the second installment of the wildly popular 2009 film, 'The Hangover,' and on Thursday night, the gang hit the red carpet in Los Angeles for premiere night with a surprise appearance from a certain scene-stealing monkey.

Crystal, who plays a drug-dealing animal in the movie, had cameras in a frenzy as she strut her stuff in a lovely, pink frock, but this fashion-forward primate wasn't the only odd appearance last night- it seems the guys made the film's premiere a mother/son date night of sorts.

Ed Helms confessed he was "scared" for his mother, admitting there would be "a couple moments in the movie" where he'd have to distract her from the racy scenes with the tactic of "leaning over and talking to her randomly."

On the other hand, Bradley Cooper had no problem bringing his mom, boasting that it wouldn't be the first time Mrs. Cooper was exposed to such bawdy humor. Cooper says he "broke [his] mother in" with 2001's raunchy cult classic, 'Wet Hot American Summer.'

All four stars of the original comedy blockbuster (which is the highest-grossing R-rated comedy of all time) are back, this time raising hell in exotic Thailand for Ed's character's wedding.

Watch the video to hear more from the cast. 'The Hangover Part II' hits theaters May 26.