Marshall tied Egdud Furhaki for most outgoing in his junior year of high school, 1996. When Lily and Marshall get married in season 2, Marshall mentions Lily had got him a shirt that read "Marshall and Lily: Rockin' it since '96", their first year of college.
When Ted is recounting his relationship with Jeanette, she is shown pulling the fire alarm in the building where Ted works, but in episode 8.15 "P.S. I Love You", it was revealed that there was no alarm lever to pull. Jeanette actually started a fire to set off the alarm.
At the art gallery, after Marshall tells the Ninja Turtle joke, he shows his left hand for the guy to give him a 'low-five' while holding the Skittles on his right hand. But in the next shot it is now his right hand asking for the low-five while his left hand is in his pocket.
The wine bottle Ted holds and announces as being some Cotes du Rhône is in a Bordeaux bottle (with shoulders).
When Ted alludes that Jeanette will be wearing a wedding dress to Barney and Robin's wedding, Robin freaks out as he runs away. However, when the wedding day comes, Robin doesn't care at all that when Lily threatens to wear her own wedding dress for the ceremony.