PEOPLE has the exclusive first-look images of O'Donnell on Mom
Credit: Monty Brinton/CBS

Things are getting steamy between Rosie O’Donnell and Allison Janney on Mom.

“I had the best time on set,” O’Donnell tells PEOPLE of filming her upcoming episode of the CBS sitcom. “Allison is the best kisser!”

O’Donnell will guest star on the Feb. 4 sitcom as Jeanine, a woman with whom Bonnie (Janney) had a romantic relationship “back when she was drinking and drugging,” according to the network – and PEOPLE has the exclusive first look of O’Donnell in character.

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Though she has come to be known for her unscripted work on television (both on The View and her talk show, which ran from 1996 2002), O’Donnell spent the past year working on the ABC Family drama The Fosters.

Mom airs Thursdays (9 p.m. ET) on CBS.