'The Office': The return of Jan, Carol and Holly (sort of)

If you've seen teasers for Thursday's (Oct. 14) episode of "The Office," then you already know that several of Michael Scott's exes will be making a return appearance.

What you may not know is why: It has to do with the reason Michael (Steve Carell) is sporting a fake mustache in the picture on the left.

(We're getting into spoiler territory here, so click away if you don't want to know.)

The episode is called "Sex Ed," and as executive producer Paul Lieberstein told us over the summer, it deals with Michael getting a cold sore, discovering that cold sores are a form of herpes and deciding that because he has herpes, he needs to inform all of his past lovers.

"You don't get to see everybody, but you will see Jan [Melora Hardin] and Carol [Nancy Carell] and Helene [Linda Purl], Pam's mom," Lieberstein tells Zap2it.

Alas, though, we won't get to see Michael's greatest love this week. "Holly [Amy Ryan] is in Nashua, so that's a phone call," Lieberstein says. Michael also breaks the news to Donna (Amy Pietz) by phone.

The good news for Holly fans, though, is that Ryan (who also stars on HBO's "In Treatment" this season) will be back on "The Office" before the end of 2010. Lieberstein says she's shooting her first episode this week, and it's scheduled to air in December.

"The Office" airs at 9 p.m. ET Thursday on NBC.

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Photo credit: NBC