Factual error: The way Barney employs the green screen wouldn't work because a camera is needed to put a picture over the screen. To the naked eye the screen would still be green. The only plausible way to make the illusion work as intended would be a regular white screen and a projector, but this isn't the case here.
Factual error: When Ted recalls his trip to Spain the map onscreen is full of spelling and geographical errors: Marida appears in Portugal but it's in Spain and should be spelled Mérida. Valencenia = Valencia; Tarrogona = Tarragona; Grenada = Granada; Pamplona is placed where the city of Bilbao is; also Sevilla is placed 140 kilometers to the left of where it really is.
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