Santa Claus is coming to town...and he has a score to settle with the Doctor.

'Doctor Who' Spoilers: Clara To Stay For Season 9? New Rumors Surface As Christmas Special Draws Near

Nick Frost will fly into Doctor Who's Christmas special as St. Nick himself, but it won't be the first time the Time Lord and the mythical toymaker have met.

Santa and the Doctor have "a beef with each other from way back," Frost informed Radio Times (via Doctor Who TV).

'Doctor Who' Spoilers: Female Writer Set For Season 9; 'Torchwood' Catherine Tregenna Returns

While some fans may be a little wary of the series' decision to bring Santa into the fold, showrunner Steven Moffat assures viewers Father Christmas will have a solid sci-fi tie in.

"It does look like the most insane moment when Santa turns up [at the end of Death in Heaven], but we haven't gone off our rockers," Moffat told Radio Times. "No, Santa is written in properly, in a science fiction way, into Doctor Who."

Described as "The Thing meets Miracle on 34th Street" the episode will include two new reality-warping monsters - the Dream Crabs and Sleepers.

Find out more when Doctor Who airs Dec. 25 on BBC and BBC America. Click the video below to see a preview for "The Last Christmas."

Tags: Doctor Who television BBC