Movie Sign is a general term used to refer to one of two things:

• The panel of three colored lights on the Satellite of Love's bridge and above the theater doors seen during host segments.

• A signal that indicates Joel Robinson/Mike Nelson and The Bots must enter the theater as the film is starting/re-starting.

The Three Lights

The panel of three colored lights consists of (from viewer's left to right) red, blue and yellow lights.

• Red Light - This indicates that The Mads are calling the captives on the Satellite of Love. Mike learns in Beginning of the End this can also be used to call down to Deep 13, and why this is generally best avoided.
• Green Light/Blue Light - This was used in a few episodes to indicate a visitor was on the Hexfield Viewscreen. Use of this light was discontinued outside of a few Comedy Central era episodes. (In seasons 2 and 3, the light was green with a green coresponding button on the panel, from season four onward, the light was blue with a purple corresponding button)
• Yellow Light - This indicated a commercial sign and was followed promptly by the show taking a commercial break.

Movie Sign

When all the lights on the panel of three lights were flashing, accompanied by a buzzer and a rumbling aboard the Satellite of Love this indicated a Movie Sign. Movie Sign means that Joel Robinson/Mike Nelson and The Bots must enter the theater. It is revealed that The Mads can cut off oxygen to all rooms but the theater or deliver electric shocks remotely if they refuse to watch the movie. When Movie Sign was activated Joel (and later, Mike) often yells "We've got Movie Sign!"

The bots know how to fake it. In the prologue to Ring of Terror they set it off, much to Joel's annoyance. In The Final Sacrifice, Tom missed the movie sign, and it had to be done a second time. Cambot waited for him.