Alyson Hannigan of How I Met Your Mother is returning to CBS to guest star on the Christmas episode of The McCarthys.

Entertainment Weekly reports that Hannigan will play Marjorie (Laurie Metcalf) and Arthur’s (Jack McGee) upstairs tenant, Pam, on the Christmas-themed episode, which will air on Thursday, Dec. 18.

According to EW, “Pam is a sweet girl who has just gone through a painful breakup and is heartbroken. In order to cheer her up, Marjorie invites Pam to join the family for Christmas Eve. Pam joins the festivities but is shocked when she experiences the McCarthys’ competitive annual gift-exchange swap.”

EW spoke to star Tyler Ritter, son of John Ritter, about how close the cast has become, despite rumors that the show will likely be cancelled.

Just In: Alyson Hannigan is returning to CBS for a guest appearance on 'The McCarthys': http://t.co/UU2AIQsUdN pic.twitter.com/ly5Bw4Yb7a

— Entertainment Weekly (@EW) November 14, 2014

“Anytime you get the six of us together, we’re going to have a blast,” he said. “The chemistry has been there from day one.”

Ritter tweeted a photo of himself recently in his Christmas attire for the episode.

I wonder if this sweater means we're shooting the X-Mas episode? First things first, #McCarthyThursdays tonight 930! pic.twitter.com/N52j3gH5pm

— Tyler Ritter (@TylerRitter) November 13, 2014

Good night to y'all, thanks for watching @McCarthysCBS and if you are coming to the taping tomorrow night, wear your red and GREENS!! 🙂

— Tyler Ritter (@TylerRitter) November 14, 2014

Hannigan is perhaps best known for her role as Lily Aldrin on How I Met Your Mother. She also starred in the cult favorite series Buffy the Vampire Slayer and movie credits include American Pie, American Pie 2, American Wedding and Date Movie.

It's x-Mas at The McCarthys !! pic.twitter.com/IHo21oIxqq

— Jack McGee (@thejackmcgee) November 10, 2014