Alyson Hannigan joins 'The McCarthys' in Christmas guest role

Former 'How I Met Your Mother' star Alyson Hannigan is returning to television with a guest role in 'The McCarthys'.

The 40-year-old actress will play Pam, Marjorie and Arthur's upstairs tenant in the CBS show's Christmas episode, reported Entertainment Weekly.

The character of Pam is described as "sweet", but also broken-hearted following a recent break-up.

In a bid to cheer Pam up, Marjorie invites her to join the family for Christmas Eve. Pam, however, is shocked at the way the family treats each other during a competitive exchange of gifts.

The episode will air on CBS on December 18.

Hannigan played Lily in 'How I Met Your Mother' and Willow Rosenberg in 'Buffy The Vampire Slayer'.