` `` Let 's Go To The Mall '' ? executives promise to introduce mother character . Carrie Underwood , Stacy Keibler and Stacy Keibler all cast in First episode . Instinct tells writer that Rachel Bilson is too obvious a choice .
`` How I Met Your Mother '' executives promise to introduce mother character . Rachel Bilson , Stacy Keibler and Carrie Underwood all cast in 100th episode . Instinct tells writer that Bilson is too obvious a choice .