Seth Rogen punched Amber Heard in the face "to get her in the mood" for their movie.

The pair co-star in forthcoming film 'The Pineapple Express' and Seth revealed they used violence as a way of bonding on set.

He said: "We did hurt ourselves when we were filming it. James Franco cracked his face open, Danny McBride cracked the back of his head open, I punched Amber in the face just to get her in the mood for things, 'Welcome to the set, Amber.' Smack!

"But it was a lot of fun. It's bonding to come and beat the c**p out of each other, you're very physical and you're in these somewhat homoerotic positions."

Seth also revealed that the actors used a herbal cannabis substitute in the film, with some of the cast enjoying it more than others.

He added to Britain's Guardian newspaper: "It's this s**t called Wizard Smoke, it's like non-alcoholic weed. I didn't like it. James didn't have that hard a time with it, but he will smoke anything. One thing about this guy, if you put it in front of him, he'll smoke it." International