Continuity mistake: During the scene when Wally gets hit by the soldier in the cafe, and Wally bumps into another soldier, causing him to go into a cake, take notice of how much cake is on him throughout the different camera shots. Also Pops (the owner) starts to wipe the cake off of the soldier's face. The amount of cake changes between shots.
Continuity mistake: When the Army knocks a hole into the front door of the Douglas home with the anti-aircraft gun barrel, notice that the position of the hole changes between shots. And when the soldiers pick the door off of Mrs. Douglas you do not see the hole. Also notice that the door is standing back up and intact, in the background, as the soldier explains to the Douglas family about the gun.