After Fred's tie gets ruined by Barney while trying to escape the Green Goose's tower, the tie reappears moments later after Fred and Barney get out from the door of the tower.
Rock Slag disappears in back of the desk at the pizza place (after Barney knocks him out) when the Chief makes a phone call and Fred leaves with Tanya.
In most shots Fred has 3 toes but in a close-up during his "A Spy-Type Guy" song, he has 4 toes to shoot a gun hidden in his boots.
When they go to Paris, they drive on the left side of the road. It's the UK who drives on the left, not mainland Europe.