Tell the group about "The Green Glass Door".
Only certain objects or things are allowed through the Green Glass Door. Start with a few examples - you can have a hammer but not nails. Books can go in the green glass door, but words cannot. You can have a spoon but not a fork. Apples can go through but an Orange definitely cannot.
Throw it open to the group to make suggestions and answer with a "Yes" or "No".
The secret criteria is that words with a double letter are allowed through.
The Moon can go through, but not the Sun!