David Alan Grier

David Alan Grier

Forced to improvise between story arcs on "Heroes" in the spring, NBC is going to, well, improvise.

The network will roll out a new improv comedy series called "Thank God You're Here" at 9 p.m. ET Monday, April 9. It will remain in the "Heroes" timeslot the following week, then move to its regular home -- 8 p.m. Wednesdays -- on April 18.

The two Monday airings are designed to give the show, hosted by actor-comedian David Alan Grier, a leg up with "Deal or No Deal" as its lead-in. New episodes of "Heroes" aren't slated to be back on NBC's schedule until later in April.

"Thank God You're Here" also shouldn't affect the current occupant of the 8 p.m. Wednesday slot, "Friday Night Lights." The network has aired only a few repeats of "Lights" this season, so it should be done for the year by then.

Based an Australian show, "Thank God You're Here" will feature a rotating cast of comedians who have to think and act on the fly. In each show, an actor will walk into a scene they know nothing about; another performer will greet them with the line, "Thank God you're here," and things take off from there.

The premiere episode will feature "Malcolm in the Middle" star Bryan Cranston, Jennifer Coolidge ("Joey," "Best in Show"), Wayne Knight ("Seinfeld") and Joel McHale ("The Soup"). Future episodes will have the likes of Jason Alexander, George Takei, Mo'Nique, Shannon Elizabeth, Eddie Kaye Thomas, Chelsea Handler, Fred Willard, Alanis Morrisette and Angela Kinsey ("The Office") acting without a net.

Fax Bahr and Adam Small ("The Jamie Kennedy Experiment") are executive producing the show with Cecile Frot-Coutaz ("American Idol"). Grier is also a producer.