The Four Guards

From Muppet Wiki

The Four Guards were featured in the movie Labyrinth. They stood guard in front of two doors. One of the doors would lead to the castle at the center of the Labyrinth, while the other door would lead to "certain death". The bottom two guards were clueless as to which door leads where. The top two guards were the only ones who knew the answer.

The Four Guards were given a set of rules about the information they held. Two of these rules, meant for the top two guards, were revealed in the film. Only one of the guards could be asked about the door. The other:

And I should warn you that one of us always tells the truth and one of us always lies. That's a rule, too. He always lies.

The Labyrinth novelization refers to these characters as Alph and Ralph and Jim and Tim.