's marriage to fiction writer Holiday Reinhorn is going strong after twelve years. What's the key to happily-ever-after bliss? 'Just don't break up,' 'The Office' star, 41, told OK! at 'The Last Mimzy' premiere in NYC on March 18. 'You have to form a partnership, and view your marriage as a partnership.' One joint project the pair share is their son Walter, 18 months. Super dad Rainn, who plays a science teacher in the family adventure flick, brought the little guy to the movie set, and told OK! 'When he sees me on TV, he says ëdada.'' Walter is in for fun times ahead. 'Rainn is a goof,' kid costar Chris O'Neil told OK! 'He almost gave me a swirly in the girls bathroom.' Um, how did he get in the girls bathroom? 'He didn't get me in there. He almost brought me in there, and he was gonna give me a swirly.'-Valerie Nome
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