Melinda Sue Gordon/Warner Bros.
05/20/2011 at 09:00 AM EDT
How do you top a movie in which a group of friends gets drugged, attacked by gangsters and has a run-in with Mike Tyson's tiger? According to Hangover
star Bradley Cooper
, it takes a very special new character.
"I remember [director Todd Phillips and I] were talking about it," Cooper recalled at a Hangover 2
press conference on Thursday. "He was saying there's gonna be this drug-dealing mule that's a monkey and it's gonna smoke, and I was like, 'How the hell are you gonna pull this off?'"
Enter Crystal, the trained capuchin monkey, who joined Cooper, Phillips, and actors Ed Helms, Zach Galifianakis and Ken Jeong in Thailand for the comedy's shoot. And Crystal (who only pretended to smoke cigarettes
) was just what Phillips needed to pull off his wild vision.
"You know, Crystal has turned out to be just a miracle monkey," Cooper said. "She's incredible. She can do anything."
Cooper toted Crystal around on his shoulder during many Hangover 2
scenes, which was fun for the actor, except for one part.
"The only downside to Crystal is that she has very long claws, and you don't want to get Crystal around an elephant," Cooper said. "There was one scene where we were walking down the street, and there was an elephant, and she sort of destroyed my shoulder."
Helms, who plays face-tattooed Stu, had his own special Crystal story. "My favorite part about Crystal is, her trainer was this guy named Tom, who was a sweet guy, but whenever he needed Crystal to do something he would literally just say, 'Crystal! Get on the table! Jump on the table! Jump on the table! Jump on the table!'" Helms said. "And then Crystal would do it. I don't know if Crystal actually understands English, or she just is able to read the energy based on what he's saying, but I found it so hilarious that her trainer would just repeat an English command over, and over, and over again, until Crystal eventually did what she needed to do."See more movie animals on PEOPLEPets.com:Reese Witherspoon Trusts Tai the Elephant 'More Than Any Other Animal'VIDEO: Meet George, the (Massive!) Star of Marmaduke