Continuity mistake: There is a scene just after Lloyd meets Beth in the bar when Mary is skiing along and looks around for Harry who is still stuck on the ski lift. The shot is comprised of a long shot of her skiing to a grey marker and then a close up of her stopping and looking around. It is obvious in the shot when she comes up to the marker that the woman on the skis has much darker hair than Mary and is her "ski double". (01:13:20)
Continuity mistake: When Harry and Mary go out on the date to the ski resort, they get into a snowball fight. When Harry is shoving her face in the snow, the first time it shows Mary she is facing one way, but when they show her again she is facing a different way. In addition to this before the camera cuts to a different angle on Harry you can see Mary's nose is bleeding immediately after she stands up. The camera then cuts to a different angle and it isn't. (01:18:21)
Continuity mistake: When Mary and Harry are talking about the "Bull-Shit" there is a shot of Mary close up where she is laughing and smiling. Look behind her and you will see a woman in a black and gold glittery dress walk past. Then when the shot changes to both Mary and Harry together the woman is instantly 3 or 4 feet in front of where she was and seems to be engaged in a conversation with someone else already - instantly. (01:06:50)
Continuity mistake: The film appears to begin in the summer. Look at the outside shots in Rhode Island when either Harry or Lloyd are driving; green grass and many leaves on the trees. As they travel further west the landscape appears to be fall. Then finally in Colorado it appears to be the dead of winter.
Continuity mistake: When Lloyd is driving Mary to the airport, at one point he says "What's the matter, nervous about the flight?" When he says this look at the white van in the rear window, it's right up next to the limo. However when the shot cuts to Mary it's already several meters behind them despite the very slow movement the limo has made. (00:04:30)