Continuity mistake: Robin says she never played any team sports in 1-6 "Slutty Pumpkin". But in this episode she talks about her relationship with her father, being on a hockey team that won a championship and she made out with her teammate.
Revealing mistake: In the front shot of Ted in front of Stella's apartment, it is painfully obvious that he is in front of a green screen and not actually on a street.
Other mistake: At the end, on the steps in front of Stella's apartment, Stella's daughter stares at the camera for half the shot.
Chosen answer: She was finally shown at the very end of the last episode of season 8, continuing into season 9. The actor's name is Cristin Milioti: http://www.imdb.com/name/nm2129662/.
Knever