Continuity mistake: In 2-21 Something Borrowed, Lily's high school boyfriend, Scooter, reveals his name is Bill, but this episode in a flashback he tells Lily his name is Jeff. (00:03:47)
Other mistake: In the credits, Jeremy Gabriel (Robin's new 'boyfriend') is shown as "Mark" but it is "Mike" throughout the episode.
Continuity mistake: Robin says that she doesn't like team sports, and so she only played tennis in high school. However, throughout the show, Robin often talks about playing hockey during school, which is a team sport.
Slapsgiving 2: Revenge of the Slap - S5-E9
Audio problem: When Lily's dad shows up at her house unexpectedly, Lily starts walking to open the door before the bell rings. (00:02:30)
Sweet Taste of Liberty - S1-E3
Continuity mistake: After Lily takes off her ring in the bar, she is seen in a later shot with the ring on her left hand.
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.
Revealing mistake: In the front shot of Ted in front of Stella's apartment, it is painfully obvious that he is in front of a green screen and not actually on a street.
The Pineapple Incident - S1-E10
Continuity mistake: When Lily says "No dibs" and touches her nose, she does it with her right arm/hand, but in the next shot, her left arm/hand is on it. (00:05:55)
Nothing Good Happens After 2 A.M. - S1-E18
Continuity mistake: When we first see Korean Elvis, Marshall has his hand on his beer. The camera cuts to Marshall and his hand is no longer on his beer. (00:12:00)
Nothing Good Happens After 2 A.M. - S1-E18
Continuity mistake: When Ted walks up the steps to Robin's apartment his bag is all creased and folded. When he arrives at her apartment it has no creases. (00:10:30)
Game Night - S1-E15
Continuity mistake: In the flashback we see Barney get handed a crumpled flyer. When we see the close up of the flier it is no longer crumpled up. (00:14:00)
The Pineapple Incident - S1-E10
Continuity mistake: When Ted is explaining to Robyn about Trudy he points at the door. Camera cuts and his arm has been lowered. (00:20:20)
Continuity mistake: When explaining why he has 2 costumes every year, the way Barney holds his drink changes instantly. (00:12:00)
Game Night - S1-E15
Continuity mistake: When Barney holds out his phone to show the video of himself with Shannon, it repeatedly switches between his left and right hands. (00:19:30)
Revealing mistake: When Barney and Ted are holding hands on the beach and it starts raining, you can see that the sand is only wet in the place where they are sitting, but dry behind them, and on the left and right side too. (00:16:35)
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.
Continuity mistake: When Barney and Ted are calling dibs on the girl at the bar, in the closeup her book cover clearly reads "Brideshead Revisited", but in the wide shot it's something else entirely, spread across several lines.
Continuity mistake: In the 7th episode of Season 5, the scenes when the "Storm-Trooper" (actually, a robot) passes by The Window do not match. The first time we see it, from the outside, as soon as he passes, Robin notices him and points towards him, but the second time, from the inside, she doesn't point at him.
Chosen answer: In a flash forward scene in Season 8, it shows him with his first born: a daughter.
XIII