( The Frisky ) -- `` How I Met Your Mother '' has me a little confused . I 've watched the show since the beginning and think it is one of the best sitcoms , evah . It 's laugh-out-loud funny and unpredictable ( Who can forget Slapsgiving or Robin 's Canadian pop single , `` Let 's Go To The Mall '' ? ) , and gets the late 20-something experience like no other show . Not to mention that Neil Patrick Harris as Barney is one of the funniest characters of all time . But , I digress . The premise of the show has been that Ted is narrating to his children how he met their mother . Only , fours years in , we still have no idea who she is . Earlier this year , the show 's executive producer PROMISED that in episode 100 , airing this coming Monday , we would finally be introduced to this elusive mother . At the same time , it was leaked that Rachel Bilson was cast for a recurring role on the show . It made so much sense : Ted and Rachel , Rachel and Ted . They 're both brunette and would look adorable together . But now new casting news is messing everything up . I just read that two other ladies of note are getting roles on the show . First up is former pro-wrestler Stacy Keibler , who will also be in the 100th episode . And Carrie Underwood just confirmed that she will be on the show this spring . So , uh , who is the mother ? My instinct tells me that Bilson is too obvious a choice , considering this is a show that 's kept us guessing for four years . The Frisky : 13 super annoying ways people abuse Facebook and Twitter . Remember how , after watching Ted and Robin 's romance begin to blossom , we got to the last second of the season premiere and Ted said , `` And that 's how I met your Aunt Robin . '' I just know we 're in for a twist here . TM & © 2010 TMV , Inc. | All Rights Reserved .
` ` How I Met Your Mother '' executives wanted to introduce mother ##hood . Rachel Griffiths , Stacy Lewis and Carrie Underwood all cast in 100th episode . Underwood tells writer that Bilson is too obvious a choice .