"I just look for a really nice ass!" the actor, his tongue in his cheek, told reporters at Tuesday's New York press conference for his new movie, The Romantics.
Kidding aside, the Transformers star, 37, says he's come to appreciate Fergie's inner beauty and the connection that's at the core of love. "You grow up and you realize it isn't just about the aesthetic," he says. "It's about whether or not that person makes you better and whether or not that person makes you happy. You're lucky if you can find it."
Duhamel's character in The Romantics isn't so lucky. Leading up to his own wedding, he's caught in a love triangle between his bride (Anna Paquin) and her maid of honor (Katie Holmes).
Filming the role made Duhamel thankful for his real-life relationship with the Black Eyed Peas singer, whom he married in January 2009. "It makes me appreciate my wedding," he says. "It makes me appreciate that I knew going in that I was with the one that I wanted to be with."
He adds: "The scary part is the idea of not knowing for sure. My character didn't know whether or not he was going to go through with it, and that's the biggest nightmare you could have, especially for a groom-to-be."