Yup, a rumor [1] from last week has been confirmed: Heidi Montag and Spencer Pratt are heading to How I Met Your Mother [2] for a guest spot in an upcoming episode.

The Hills [3] stars are on set to film their roles this week, and the episode will air in January. Series co-creator Craig Thomas joked to E! that "one of them is the Mother," but that's so obviously not true. What is true: Their part of the episode revolves around poop. How . . . oddly fitting.

Writes E!'s Kristin Dos Santos, Marshall will be lacking an appropriate place to do no. 2 at work. Then:

According to CBS, Spencer and Heidi will be playing magazine cover versions of themselves as Marshall searches for a place to "read a magazine." Speidi will taunt and tease Marshall from the confines of his current copy of Them Weekly.

Heh, Them Weekly.

Anyway, How I Met Your Mother showed it can handle big-name guest stars well with the Britney Spears episodes [4] last Spring. But I'm curious to see whether Heidi and Spencer will draw viewers to the show — or repel them. Do you think this is a savvy move? Or does it seem risky to give these two even more exposure?

Photos courtesy of CBS [5] and Source [6]