Super Demo World: The Legend Continues
Super Demo World: The Legend Continues contains 10 worlds, 84 levels and 120 exits. Since this hack is a "demonstration", the levels can vary wildly, with several different themes present in the game, many of which were nonexistent in the original SMW. Two of the harder levels are Pipe World 2 (because of a frustrating pipe maze) and Big Boo's Tower (due to 100 floors)
Crystal Cavern Secret Messages
In Crystal Secret, Crystal Cavern 2, Crystal Cavern 3, Crystal Cavern 4, and Crystal Cavern 5, you'd get an interesting series of secret messages by using the message block found in Water Secret. For all levels except Crystal Secret, you'd need to disable all layers except Layer 3, as well as the HDMA emulation switch. They all hint at Lunar Magic's compatibilty to Super Mario World: Super Mario Advance 2.