Ken Jeong is in “Pain and Gain” for only a few scenes, but the doctor-turned-actor’s Johnny Wu, a cheesy self-help guru, sets the events of the film in motion when he encourages Mark Wahlberg’s Daniel Lugo, a Wu fanboy, to be a “doer,” not a “don’ter.”

Your character isn’t in the film for long, but he’s a constant presence.
My character plays a very small part of this movie, but with anything I’ve ever done in my career, [I’ve learned] there’s no such thing as a small part.

You worked with Michael Bay on the last “Transformers” movie. By comparison, “Pain and Gain” seems small.
This is a passion project he had since ’99. … He described it to me and described my character [and] sight unseen, I said, “I’m in.” I just would do anything for Michael Bay.

Did you watch any self-help seminars or infomercials to prepare for the role?
I did study tapes, and I looked on YouTube for Tony Robbins and things like that. There are good motivational speakers and bad ones, and I wanted to play a bad one. And I wanted to say stupid, empty things with authenticity. How do you yell empty catchphrases with such gravitas? That was the goal.