Continuity mistake: When Stephanie runs to the shelf to pick the second volume of the encyclopedia the amount of cats increases/decreases randomly between shots. Also, the amount of books and their position changes.
Continuity mistake: When Stephanie shows her ants and rabbits to Number 5, the amount of cats on the shelf behind suddenly increases between shots.
Continuity mistake: Ben brings a jacket to Newton, who looks at him. A shot later he is looking at the opposite way.
Continuity mistake: During Frank's second visit to Stephanie's home the stack of pancakes J5 is holding decreases from a load to a few over several shots. (01:04:50 - 01:05:20)
Continuity mistake: At the beginning of the movie when the "Red Army" approaches, the tank has his barrel locked in a transportation brace. As soon as the tank fires back, the brace is gone.
Continuity mistake: A cat is ontop af a boiling saucepan in Stephanie's kitchen, yet it seems to be rather comfortable. Brave cat. [It is dry ice in the saucepan, so all animal lovers don't worry.] (00:31:45)
Continuity mistake: At the start of the film, Howard is talking to a woman and it's lovely and bright and sunny. Yet just a few seconds later we get a shot of the sky and there are lots of black clouds and it starts raining. (00:07:35)
Continuity mistake: In the scene right after Number 5 almost drives the snack wagon into the lake and the Nova guys are shooting him, you clearly see him get shot in the hydraulic pistons which control his head motions. Yet, in the next scene (in the truck) Number 5 comfortably moves his head.
Answer: There were always 5. You see the 5 during the demonstration. Then, before the lightning hits, we see 4 of them in line, but number 5 was still attached to the generator and not in line. When they go inside, there's a weird cut that makes it look like only 3 made the turn, but if you watch closely you can see there's 4 followed by number 5.
Bishop73