This is a spoken game often played at camps, or at least that's where I learned it. It's one of those where you try to figure out what the rule is as you play. (Looking it up or asking someone who does know is not allowed - and sure, if you do it we may never know, but you'll know and hopefully you'll feel guilty so just don't cheat ) Anyone who does know the rule, don't say it!
I am going to bring a puppy through the green glass door.