In one scene Jack and Karen are in the coffee shop talking about Jack's nursing class and Nurse Carver. Jack then says "What a rotten day...", and heads off - walking to the exit and opening the shop door. It then cuts back to a shot of Karen, however Jack is now stood right back next to her.
When Will and Grace are in the American candy store, all the counter display units which have Brand names on them, are covered in small pieces of colored tape - assumedly to somewhat hide them and prevent product placement.