Rachel Bilson, who played Summer Roberts on the The O.C., has been booked for a guest spot on the 100th episode of How I Met Your Mother creating speculation that she is the mother. Bilson’s rep confirmed the gig to Buddy TV but wouldn’t give up any details. Bilson wouldn’t be the obvious choice for mother but some recent hints have fans believing she’s the one.

Last month, the show’s executive producer, Craig Thomas, told EW that the milestone episode (airing in January) would feature “some serious mother action,” adding, “It’ll be the closest Ted’s ever come to [discovering who she is]. He’s getting a step closer every episode this season, and episode 100 [we] kind of go bananas with it.”

Bilson is also starring in New York, I Love You which premieres tonight in NYC and opens in limited release on Friday.

Of course, its hard to believe that they would reveal the mother already. The show is going strong and it seems way to soon to wrap up the major plot mystery. What do you think of Rachel as the mother? Do you think its too soon to reveal her identity?