Continuity mistake: When Number 5 gets out of the truck it is no longer hanging over the edge of the cliff. It has moved inland by several feet. (00:46:45)
Other mistake: When Johnny is changing his arm in the back of the Nova truck, it's quite obvious that the new arm he 'attaches' isn't realy attached at all. (00:51:50)
Continuity mistake: Johnny flicks around the radio stations and tunes into 94.1 and there is some music - he tries another station and then comes back to 94.1 and it is already into the first chorus of the "Who's Johnny?" song. (00:54:25)
Factual error: When Number 5 is watching Saturday Night Fever, he is watching and grooving to the climactic dance-off scene in Saturday Night Fever on TV. Stephanie then enters and the scene on TV shifts to one much earlier in the movie he's supposedly watching. (00:57:15 - 00:59:30)
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)
Revealing mistake: When Frank takes the orange juice from the tray Johnny 5 is holding, the tray moves with the glass for a second. This is because the orange juice glass was glued to the tray, so Johnny wouldn't drop it. (01:05:25)
Visible crew/equipment: When Johnny is blocking Frank's gunshots with pieces of Frank's car, you can see the wires attached to Johnny's arms for the puppeteers to control him. In the last one, you can even see one of the puppeteers' hands. (01:06:25 - 01:12:21)
Other mistake: The tree used to hold up Number 2 is very thin and weak looking, yet it supposed to be supporting a 400lb robot. Strong tree. (01:13:25)
Revealing mistake: Some shots used in the scene where Johnny runs from the Nova helicopter were shot using the small toy version of Johnny. There were no mountains in the area and a small version was filmed heading towards some big rocks with the camera on the ground to give the impression they were in a mountainous area. (01:30:15)
Continuity mistake: As Johnny runs from the Nova helicopter his chest plate falls down, in the next scene, it's back up again. (01:31:05)
Visible crew/equipment: When Newton is playing with the robot arm and the piano you can clearly see wires attached to the top of it controlled by the puppeteers.
Continuity mistake: When Johnny 5 nearly drives the snack wagon over the edge to where it is hanging, it appears to have miraculously moved right back from the edge, making it look like he never went nearly over in the first place.
Revealing mistake: When Number 5 is leading Number 3 into the toilet and moves at the last minute, you see Number 5 falling over, but in the next scene, he's perfectly fine.
Revealing mistake: When Frank is knocked down with the tray, the arms of the person operating Johnny 5 are visible when the robot turns to run.
Continuity mistake: Number 5 picks up mud and throws it at number 1's face. But from there on, Number 5's hands have no mud on them. We never see Number 5 clean his hands, so were did the mud go?
Continuity mistake: The amount of mud on number 1's face changes to nearly nothing to loads.
Visible crew/equipment: When number 5 falls off the bridge you can see a thin rope attached to him, either used to activate the parachute, or used as a guide wire to keep the robot stable while falling.
Revealing mistake: After Johnny blocks the gunshots from Frank, he begins to flip a coin and imitate John Wayne. You can see the thin wire connected to the coin on the left side of it.
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: Crosby's tie was open after the jacket was on, then crossed as he says "but just one dance"
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