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From the Houston Chronicle:

A lot of people were surprised by Combs' presence in the cast. Though he says he started seriously studying acting eight years ago, he'd had only a couple of acting jobs before that — small roles in the movies Monster's Ball and Made. ...

What happened, see, is that Combs' acting coach suggested he read for the part of Walter Lee Younger, which was played by Sidney Poitier in the 1961 movie.

"It sounded crazy to me," he says. "I'd never done live theater. I'd never starred on the stage. I was like, 'I don't think so. Let me get a couple more films under my belt, and then maybe I'll do something like that.'