The 26-year-old actress was left "gushing blood" after an accident on set, and now bears a prominent scar.
She told FOX News: "I've had so many injuries! I actually ripped out a little piece of my neck off in 'Forgetting Sarah Marshall'. It happened when we were in the water.
"Jason Segal is holding my neck. He's holding it because I'm bleeding - you only see half my neck. The other side is gushing."
Mila is not the only star to get injured on set recently.
Rose McGowan had part of her elbow removed after she injured it filming a stunt for new action film 'Red Sonja'.
The former 'Charmed' star explained: "I had surgery and they took part of my elbow out. I had really bad nerve damage from doing stunts - I do a lot of my own stunts.
"I could no longer use my arm, but now I can hold a fork and drive so we're working our way up. It'll probably be another six months of rehab."
