The new Pixar movie Inside Out is about the emotions swirling around in an 11-year-old girl's head. "Joy was the last emotion to be cast," says director-cowriter Pete Docter, "and it was the most difficult of any of the characters to write for because she had a tendency of being really annoying." Joy is a relentlessly chirpy cheerleader, he says. "You wanna sock that person!"

'Inside Out''Inside Out' brings together Joy, Fear, Anger, Disgust and Sadness

Enter Amy Poehler, ideal casting for the role after her years as the happy control-freak Leslie Knope on Parks and Recreation. She was thrilled by the project: "From the minute they told me I was like, this is the best movie ever made! And it will be the only good movie I've ever been in. And I can't believe I'm in it."

She has huge respect for everything Pixar does. "They are like the gold standard," she says, "so if they had asked me to do anything I would have said yes. That's not a good negotiation tactic, by the way, but it's true."

Watch the trailer for 'Inside Out' here:

Poehler admits that some of her "energy and bossiness" make her perfect for the role of Joy. "I do think she just likes living in the moment," she says, "and maybe I like to think that I do that too. But I aspire to be more like Joy. I think that the characters in the film get all of the range of emotions. Everybody feels anger, fear, sadness, joy - each with their own journey. But I love love. And I love sadness and joy living right next to each other. And this film is certainly a celebration of that."

More: What are the critics saying about 'Inside Out'?

She also feels that the movie works beyond its somewhat gimmicky set-up. "On one level, it's just this really funny Pixar movie that is filled with emotion," she says. "But it's also about this cast of characters who don't belong together but go on this journey to change a life. And the bigger perspective is it's about very big conceptual things like what makes you happy and why do we try to always be happy? Why do we do our kids a disservice while protecting them from pain and resistance? That said, the experience was a joyful one."