Here’s a quick look at some of the casting announcements made recently:

Glee: Singer Olivia Newton-John is the one creator Ryan Murphy wants for his show. In the upcoming episode, the Grease star will perform a duet with…Sue Sylvester (Jane Lynch). The two will team up for a rendition of Olivia’s classic “Let’s Get Physical.”

How I Met Your Mother: She knows how to front an awards ceremony, but does Carrie Underwood know how to act? This March, the country singer will be given a chance to test her comedic timing on the CBS comedy. Underwood will cameo as a pharmaceutical sales rep who has a romantic connection with Ted. (How many potential “mothers” could this guy possibly have?)

Law & Order: SVU: Hey - Julia Roberts once guested on the L&O franchise, so why not Sharon Stone? The Oscar nominee is slated to appear in four episodes as a former cop-turned-prosecutor. She’ll make her entry sometime in April. Meanwhile, The Beautiful Life‘s Mischa Barton has also been tapped for an hour in March.

Mercy: James Van Der Beek has been recruited for a recurring part on the NBC series. The former Dawson’s Creek star will play Liam West, a “cocky, womanizing, and manipulative” ICU chief. The role could be upgraded to regular status.

Desperate Housewives: Actress Julie Benz will tackle more lighthearted fare on the ABC series. The Dexter star will be featured as a highly educated woman who is also a stripper. Benz will work the pole for at least three episodes. Look for her starting in February.

Castle: Dana Delaney will soon be reuniting with former on-screen husband Nathan Fillion—but as a different character, and on a different show. Delaney has been cast in a two-episode stint as a federal agent that will air on back-to-back nights beginning March 21. The first episode will come right after a showing of Desperate Housewives.