Behind the door would be in entrance to a parallel universe where dog are cats and cats are dogs. And that is just the beginning. The gravity is up side down so it pushes you off the planet instead of in. And the planet spins really slow so the people don't fly off at a billion miles per hour. Then people build walk ways and houses upside down and if you accidentally step off a walk way you will fly out into space and die. Well luckily the government of this parallel universe does everything in their power to not let this happen.