SO, THERE I WAS ON THE SET OF JOHN Waters’ “Pecker” last fall, taking notes for a magazine story, when the director asked whether I wanted to pull a George Plimpton and act in the film. Fine. As what?

The title character of “Pecker,” John Waters’ 13th film, is a teen-age sandwich-maker in Hampden who is nicknamed Pecker because as a child he pecked at his food. But just as the film’s title flashes ...