The cast of 'Thank God You're Here' performs a skit.

1 of 7
The stars of a new comedy show are teaching Oprah to do something she's never tried before—improv! On NBC's Thank God You're Here, guest stars are put into costumes and thrust into unrehearsed, unscripted comedy scenes. Armed with their acting skills, they make up their lines as they go...trying to be as funny as possible.

The show's host and producer, comedian David Alan Grier, starred for four years in the hilarious Emmy award-winning sketch comedy series In Living Color—but he says his new show is even more fun!

"It's the unknown, which is very rare on television, where we're taking a chance with each and every sketch," David says. "It's an adventure. I watch, and we really don't know what's going to happen."