Bradley Cooper 

The actor found filming the third and final instalment of the comedy an emotional experience and is disappointed he won't be reunited with his co-stars for another booze-induced movie misadventure.

Speaking at the Los Angeles premiere of 'The Hangover Part III' at the Westwood Village Theater on Monday night, Bradley sighed: "It's a little sad. It's bittersweet."

Quizzed about the lesson he'll be taking with him, he replied: "Gratitude."

The film sees the Wolfpack gang - comprised of Bradley, Zach Galifianakis, Justin Bartha and Ed Helms - head back to Vegas to settle one final debt and decide to put their wild days behind them once and for all.
Zach, who plays clueless Alan Garner in the films, revealed he would miss the behind the scenes banter with his co-stars and the constant teasing.

He said: "Without sounding too corny, there's a lot of laughing going on on set. There's a lot of camaraderie. There's a lot of making fun of each other. I will miss that.

"I won't miss getting made fun of. But I love making fun of the other guys. We click."

The bearded funnyman also teased he was only able to keep a straight face on set because he's deaf, before confessing he has actually become jaded by the jokes.

Zach added to the USA Today newspaper: "Things that make me laugh are few and far between. I'm a little bit too jaded. It's easy for me not to laugh sometimes."