Everyone sits in a circle, and each person asks the leader/counselor if they can bring an object through the door, and the leader answers yes or no. You go around the circle until most of the people seem to have figured out the pattern. The pattern is that they can only bring things that are words with doubled letters in them
Things you can bring: Jelly
Water balloons
Kittens
Things you can’t bring: Jam
Watercraft
Cats