The wolf pack is back!

In a new trailer for The Hangover Part II, best buds Phil (Bradley Cooper, 36), Alan (Zach Galifianakis, 41) and Stu (Ed Helms, 37) make Doug's Las Vegas bachelor party look like child's play.

The sequel is relatively similar to its 2009 predecessor: After Phil, Alan and Stu throw a wild bachelor party in Bangkok, they're forced to piece together their night after being roofied during their boys' night out.

Two major differences? Alan wakes up with a shaved head and discovers that Stu has passed out in the bathtub -- with a freshly inked tattoo on his face.

The rest of the cast -- including Doug (Justin Bartha, 32) and Mr. Chow (Ken Jeong, 41) -- return for the laugh-out-loud sequel, as does Mike Tyson, 44 (who plays himself).

Though 58-year-old Liam Neeson makes a cameo in the sequel -- he replaced Mel Gibson after the cast forced director Todd Phillips to drop him from the film -- his scenes do not appear in the trailer.