When Peter waits for Big Fat Paulie, he has on a watch and tie, which Paulie spits on. When we see them enter the theatre, Peter has no tie or watch on.
When Peter is waiting for Big Fat Paulie at the theater, he is wearing a white shirt buttoned to the collar, a black tie, and black pants. When they enter the theater, Peter is wearing his usual attire: a white shirt unbuttoned at the collar, no tie, green pants. When they leave the theater, Peter's collar is buttoned, the tie has returned, and his pants are black again.
After coming home with Paulie while in the kitchen Peter has a watch on, the watch wasn't on before and isn't seen again.
When the two British are staging a "drive-by arguement", the car's seating is correct, but he is driving on the wrong side of the road.
The hitman, the groom, had no idea Lois would be at the wedding so there was no way he could have planted the car bomb.