When turning on the Rocket Camcheat and shooting a rocket through the Cape Canardo entrance towards the right, you can see the inside of Juliette's closet.
If you hug the wall and walk through the Viggo A Gogo entrance, you will walk through the entrance boundary lines. There is water you can swim in, too, but only a very small distance, due to a forcefield that is supposed to end the boundaries of the map. The only problem is, you cannot get out of the water.
Bungalow can access Roofus' rooftop - there is a hidden floor near the picnic table on the balcony. If you get inside the chimney, you will get stuck, and the only way to get out is by restarting the game or fluffing yourself. However, he can walk out in the PS2 version, removing the need for restarting the game or fluffing yourself.