Continuity mistake: During the "shower scene" when Dermot comes out naked and Debra looks away with her hand on her mouth, her hands keeps changing places. Facing her, she puts her hand on her mouth, but in a side shot, she has her hand over her eyes. Then when facing her, she has her hand over her mouth again.Karoo
Continuity mistake: Just prior to the wedding (near the end), when Debra and Dermot are outside the church standing beneath the arbor, she is holding her floral bouquet. When they enter the church, the bouquet is gone; Once she's walking down the aisle, the bouquet reappears.
Continuity mistake: The dance lessons take place the morning after stags and hens, making it Friday. But they're suppose to be two days before the wedding, so they should have been before stags and hens on Thursday. When Kat arrives at the cocktail party, from the airport, her mother gives them the itinerary. Tomorrow is young people in the park, followed by stags and hens, Friday is the picnic, then the rehearsal dinner. During the party, she's talking to her sister at the bar, after a stumble with the fiancee, Amy says they have dance lessons two days before the wedding.
Factual error: When they are leaving the USA to fly to London and are checking in at the airport, a guy walks past in an Easyjet ground handler's uniform. Easyjet doesn't operate in the USA - clearly filmed in London Gatwick airport.