Okay Awesome - S1-E5
Continuity mistake: When they first arrive at the club we see Barney, in close up, undo some of his top shirt buttons. A few seconds later, he is seen in the background with his shirt buttoned. (00:05:30)
No Tomorrow - S3-E12
Continuity mistake: Towards the end, when Ted says, "You just yelled at me", look at Marshall. He's about to take a sip of his drink, but when the camera cuts to a different angle, the mug's nowhere near his lips anymore.
No Tomorrow - S3-E12
Continuity mistake: Towards the end, when Marshall's yelling at Ted, Ted says, "You yelled at me". When the camera angle changes, Marshall's hand changes position.
The Chain Of Screaming - S3-E15
Continuity mistake: When they're all sitting in the car listening to Marshall's story, Robin's ice cream changes between shots.
Continuity mistake: When Lily is making the layered salad, in some shots the layers are defined, but in others there is much more mayonnaise running between the layers. (00:07:30)
Continuity mistake: In the scene where Ted goes over to Robin's apartment to yell about their breakup, Robin says "You shaved" and "I liked the beard," implying that this is the first time she has seen Ted since he shaved. But the night before she was in the kitchen at his apartment asking if he was okay with her dating Gael. At that point Ted had already shaved. (00:17:45)
Other mistake: There is absolutely no reason for Ted to hang around underneath his apartment window while Jeanette is throwing stuff out of it. Any sane person would know that there is a very high chance of getting struck by the myriad of Ted's belongings that are wantonly chucked out onto the street. He's not trying to collect/catch anything because he is turned away from the building, and is not paying attention to the items that are being thrown out.
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