Amanda Seyfried feels like she has ''won'' if she makes Justin Long laugh.

The 'Ted 2' actress adores her boyfriend's sense of humour so is pleased when she manages to live up to his comedic standards.

She said: ''He's one of the funniest people I know. He makes me laugh and sometimes I make him laugh.

''When I do, I feel like I've really 'won' because he's a born comedian.''

And the 29-year-old beauty was thrilled to be cast in 'Ted 2' because she knows she can make creator Seth MacFarlane - who previously cast her in 'A Million Ways to Die in the West' - laugh.

She told Marie Claire magazine: ''One of my favourite things about my relationship with Seth is that I make him laugh.

''Maybe he's just laughing to make me feel good, but I genuinely seem to make him laugh and that brings me a good amount of joy.''

However, Amanda is worried about taking over the female lead from Mila Kunis.

She said: ''I'm convinced people are going to go, 'Where's Mila?' and listen, she's got a lot of fans.''