Judy Greer felt like an ''ass'' whilst pretending to be a chimp in 'Dawn of the Planet of the Apes'.

The 38-year-old actress plays queen of the apes Cornelia in new film 'Dawn Of The Planet Of The Apes' and revealed that she got into the role by monkeying around on set.

Speaking to the Metro newspaper, Judy laughed: ''We did some improv with me playing an ape that the ape guru Terry Notary filmed on his iPhone. It was so weird.

''You just have to not think about what you're doing, because if you start to think about it even a little bit, you feel like such an ass.''

The 'Two and a Half Men' star admitted, however, that she had the full support of her partner Dean Johnsen - who is a massive fan of the 'Planet of the Apes' movies.

She explained: ''I love the 'Planet Of The Apes' franchise. My husband's such a big fan, it was sort of, 'If you can't beat them, join them'. He's so happy I'm in the film.''

Greer has a long list of film credits to her name, including appearances in '13 Going on 30' and 'Love & Other Drugs', but this is her first role as a leading lady and she's revealed it was a conscious decision to move away from supporting roles and into the spotlight.

She added: ''There did come a time when I also decided I didn't want to play the best friend any more.''