Continuity mistake: When Will and his date are having dinner at Will's flat, will pours his date a glass of wine into an empty glass that the date is holding out. When the shot changes the date is holding a full glass near his chest, and when the shot changes again, Will is still filling it up.
Continuity mistake: When Karen is the bar, about to pay 'Smitty,' she takes out her purse, takes out her credit card and places her purse on the barside. In the next shot the purse has vanished and the credit card is suddenly in 'Smitty's' hands (00:32:35)
Continuity mistake: When Jack is lying on the table, with the huge bowl on his face, the position of the boxes behind him on the table changes a few times. In one shot they're half hanging off of the table, in the next shot they're fully on the table etc. (01:08:15)