An ER show source confirms that George Clooney will reunite with Julianna Margulies in an upcoming  storyline that also features Susan Sarandon.

The latter star will make her ER debut as a grief-stricken grandmother, stunned over the death of her grandson.

Executive producer John Wells has revealed that Clooney will reprise the role of Doug Ross on the March 12 episode.

"If you're a fan of ER, you won't want to miss this one," said Wells.

Meanwhile, Shane West will return to the NBC drama on March 19.

Said an ER insider: Ray's return "disrupts Neela's equilibrium."

Matt Richenthal is the Editor in Chief of TV Fanatic. Follow him on Twitter and on Google+.