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: In a flash forward scene in Season 8, it shows him with his first born: a daughter.
XIII