i think you should do the cast of SMB all dressed up as the cast of The Rocky Horror Pictureshow. Have Bowser in the Frankenfurhter getup, put some koopahs rocking the Riffraff and Magenta thing, Luigi as Eddie, Mario and the Princess as Brad and Janet, Toad as Dr. Everett Scott.
You can still call the whole thing, "Welcome to the Time Warp" - just redesign sets of Rocky Horror to look like the 8-bit levels you already have. Dining hall, lab, bedroom, foyer, camera room, whatever. Then you can use the character sprites all over it acting out key scenes from the movie:
Toad sets the scene, Luigi out of the fridge, Koopa greets the guests, Bowser with Peach, Bowser with Mario etc.
The pipes will represent giant phallus-es...phalli...---Deutsche Frankfurters---.