Other mistake: When Marshall brings the large photo of The Captain into the apartment, he claims he took the photo the last time that The Captain picked up Zoey, but the background of the photo is not the inside of a vehicle.
Other mistake: Robin says she burned the dinner because she mistook the temperature scale on the oven for Celsius. However a given temperature above -40 is always higher in Fahrenheit, so by assuming the oven to be labeled in Celsius she would have undercooked the food. For example: If the directions were to cook at 400°F, she would set it around 200°F (thinking the oven was Celsius.) If the instructions were to cook at 200°C, she would still set the oven to 200°F, undercooking the food in both cases.
Other mistake: When Marshall returns from Minnesota, he approaches Lily lying on the couch from the kitchen area rather than from the door, and Lily still acts surprised to see him, even when he was obviously already in the apartment with her.
Legendaddy - S6-E19
Other mistake: When Barney is trying to take down the basketball hoop, using the screwdriver, he never actually removes any of the screws.
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