In the episode, "Dr. Yes", when Max and "99" supposedly hear cries for help coming from the two men's trailer:

1) Look when Max and "99" first enter the trailer,you should see a white closet-like door just to the right of the entrance.

2) Now, when the men close the door on Max and "99," the walls start to close in. Look at the walls, they are all black!! (No white closet door, which would be on the left side, due to the angle of the shot.)

3) OK, so our heros save themselves and exit the trailer.

4) Remember that white door? It's back!! And if you look carefully, you can see all the components of a camping trailer (I.E. bunks).