Is Rachel Bilson The Mother on How I Met Your Mother?

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 …