Kevin Hart and Josh Gad, costars of the new comedy "The Wedding Ringer," have very famous pasts in live performance. Hart is arguably the most popular standup comedian on the planet, and Gad earned a Tony nomination for his starring performance in the original Broadway production of "Book of Mormon." 

We interviewed both actors about the biggest stars they ever saw attend one of their shows. Gad reflected on times when both Oprah Winfrey and Barbra Streisand sat in the front row of "Book of Mormon."

"You sort of freeze when you first walk out, especially with 'Book of Mormon' in the Eugene O'Neill Theater. You can see everyone in the audience, pretty much," he told us. "With Barbra Streisand, there were two or three times where I sort of fell apart and forgot my lines."

Hart, meanwhile, says his best sighting was Shavar Ross, a.k.a. Dudley from "Diff'rent Strokes" -- but he added a strange anecdote about Oprah at his own home.

"Oprah came to my house and shut my house down. She interviewed me at my house. Oprah was like, 'Kevin? Nobody in or out of the house. Phone lines gotta go off. Security needs to go around the perimeter.' No one could come in or out of my house! I asked whether I could go to the bathroom in my own house." 

"The Wedding Ringer" is in theaters January 16.