Continuity mistake: In this episode we learn that Barney doesn't know how to drive. But throughout the whole series there are reference that he actually does, such as: In 'Come On' (22nd episode 1st season) : Penelope says to Barney: "We had sex twice in your car." In 'Moving Day' (18th episode 2nd season) : Barney drives away with Ted's rental van. In 'The Bracket' (14th episode 3rd season) : Barney stole Holly's SUV as they were camping.
Suggested correction: This has been corrected before. Barney does not know how to drive at the time of the subway strike in 2005, but does learn how to drive at some point shortly after that. And it's not until Moving Day (the very episode after this) that we see Barney driving. He does not have to drive in Come On, he just has to own a car.
First Time In New York - S2-E12
Continuity mistake: During Ted's second flashback to how he lost his virginity to Molly (the real story), as Molly gets out of bed you can see she's already wearing pants, but after we cut she stands up and starts putting them on.
Continuity mistake: In the car, just after Barney discovers they are not headed for Atlantic City, the DVD screen that has been hanging down from the car roof is suddenly stowed away between shots.
Continuity mistake: When Barney is in the Professor's office, we see the professor put a red pen down on her desk and her hands are then empty. In the next shot, she suddenly has a blue pen in her hand.
Continuity mistake: When Lily's mother is looking at the gift Lily has just opened, the blue bow on the gift vanishes and then reappears between shots.
Continuity mistake: When Ted is giving up with Marshall's best man speech he is holding a pen in his hand as well as a beer bottle. In the next shot the pen disappears and he is just holding a beer bottle. In the next shot the beer is on the coffee table and Ted drops the pen onto the coffee table.
Monday Night Football - S2-E14
Continuity mistake: When the gang are about to watch the Super Bowl, Marshall is holding a chicken wing which vanishes from his hand when the camera angle changes.
Monday Night Football - S2-E14
Continuity mistake: In the classroom, Marshall squirts juice on to the boy's clothes then puts the juice pouch flat on the table. In the next shot, the pouch is standing upright.
How Lily Stole Christmas - S2-E11
Continuity mistake: When Ted, Robin and Barney are having a meal at the bar, we see Robin lift her drink to her mouth, then the shot changes to another angle and we see her lift the drink again.
Continuity mistake: At the courthouse, we see Marshall, Lily and Barney walk around the corner towards the bench twice, from two different angles.
Continuity mistake: When the gang are drinking a toast to Ted at the end of the episode, Robin's glass of champagne moves from her left to her right hand instantly when the camera angle changes.
Continuity mistake: When Robin and Ted are at the bar planning their weekend away together, the level of beer in the glass next to them goes up and down between shots. (00:10:00)
The Scorpion and the Toad - S2-E2
Continuity mistake: In the scene where Lily and Marshall are talking outside the bar, the same extra (a guy in a blue plaid shirt with a denim shirt over the top) walks past Lily twice, going in the same direction both times.
First Time In New York - S2-E12
Continuity mistake: At the airport, Lily and Robin are talking off to the side away from others. During the scene, the cameras shoot from in front of the two actors and from behind Lily. From the frontal view, Lily's two headbands are white and gold-jeweled. The white headband is closest to her forehead. When the camera shot switches from front to behind, the headbands are switched on her head. The gold one is now closest to her forehead and the white one is behind.
Suggested correction: If you look closely, you can see that the headband is actually symmetrical, so the black strap is on top and in the middle of a larger white headband and never changes. (camera angle makes it often seem both from the front as from the back as if there is no white part behind the black).
Continuity mistake: In the scene at the hotel bar, the red straws lying on the table next to Ted change position between shots without being touched.
Continuity mistake: In the scene at the bar where Robin is describing looking after Marshall as being like having a baby, Barney's drink moves from in his hands to on the table and back again instantly between shots. (00:06:30)
First Time In New York - S2-E12
Continuity mistake: When Robin is talking to her sister Katie in the Empire State Building lobby, Katie's bag moves between shots. Sometimes she wears it with the strap hanging straight down from her shoulder, in other shots the strap goes across her chest like a messenger bag.
How Lily Stole Christmas - S2-E11
Continuity mistake: When Ted, Robin and Barney are at the bar, discussing the fact that Barney is ill, the level of the drink in Robin's glass goes up and down between shots.