A fan-made custom stage based on Clock Town from The Legend of Zelda: Majora’s Mask was recently created and released for Super Smash Bros. for Wii U. This particular stage is taken straight from the fan-game Super Smash Land where it appeared in a Game Boy-styled 8-bit form. Adding this stage into your game will have it replace the Omega version of Pac-Land.
Super Smash Bros. for Wii U hacking has taken off in recent months after a Wii U exploit made it easier and much more accessible to edit the game’s files. Various other hacks have also been released by a multitude of players. These include new skins and costumes for characters, moveset changes, and stage edits. You can find an increasing number of those mods here.
Smb123w64gb, the guy behind the new Clock Town stage, has also released two other stages. You can see videos of his Dr. Mario stage and his remake of the Metal Crystal stage from the original Smash Bros. below.