Ashlee Simpson and Husband Pete Wentz to Guest Star on CSI

Ashlee Simpson-Wentz and Pete Wentz attend a New Year's Eve celebration on December 31, 2008 in Las Vegas, NV.Us Magazine

Ashlee Simpson is heading back to work for the first time since welcoming son Bronx Mowgli -- with some help from husband Pete Wentz .

The new parents have signed on to guest star on CSI: NY, sources tell Entertainment Weekly.

Check out what Ashlee Simpson used to look like.

Although a show rep won't comment, EW claims the two will be playing "Bonnie and Clyde wannabes" on the March 18 episode.

See what a body language expert said about Ashlee and Pete.

It must be tough for Simpson to leave her newborn son.

See what Ashlee Simpson looked like pregnant.

"Motherhood is the most fantastic experience I have ever been thru," she blogged last December. "Bronx makes me laugh and smile everyday!"