The pair star together in 'Pitch Perfect' and Anna found her 26-year-old co-star so funny, she reverted to unusual techniques to stop herself ruining scenes by giggling.
She said: ''I did a lot of weird stuff so we wouldn't mess up takes ... stepping on my own foot, biting my tongue.''
Anna also revealed she can relate to her character Beca, who joins an all female a cappella group.
She added to Us Weekly magazine: ''I used to sing in the shower. But I got enough sarcastic clapping from my roommates that I broke the habit.
''Now I still sing in the car like a dork. I hope if people see me it just makes them smile.
''I don't like performing in front of an audience but music is such a part of me that if I couldn't sing I'd feel paralysed.''