Nick Apollo Forte was an overweight, over-the-hill lounge singer when he was cast to play a lead role in Woody Allen's Broadway Danny Rose (1983). How did Forte, who had never seen a Woody Allen film in his life, get a role for which he didn't even ask to audition? A casting agent in search of "an overweight, over-the-hill lounge singer" happened to spot Forte's picture on an album -- in a record store bargain bin.
[Sadly, Forte's luck didn't last for long. Even though Allen made Forte's song "Agita" (Italian for "indigestion") the film's theme song, he never acted in another film.]