Hi, Marly! I directed a production of Alice jr last year. We built a 2x2 base on casters, framed it in to create 6 ft tall sides. We then created a 'door' for each side. One side was the very small door which was painted and the rest of the side painted black as the void, one side a regular sized door and the third a giant keyhole. The small door and the regular sized door each had a 'head' sized hole for our 'doorknob' character. He sat inside of the piece and a stagehand turned it throughout the number where appropriate. As they did, he poked his head out of the correct door. When it was time for Alice to swim through the keyhole, he exited out the back, the door was turned so the audience only saw the keyhole which had a black curtain veiling the doorknob's exit and she swam through. It was very effective and allowed us to get the door set piece off in time for the next number. Audra