Mewtwo's Custom Moves

Although Mewtwo has no Custom Moves in Super Smash Bros. for Nintendo 3DS and Wii U, it has been revealed that Mewtwo was originally planned to have them and that partial versions of his Custom Moves exist on both systems.

Wii U
Mewtwo's Custom Moves can be unlocked in the Wii U version by importing a Mii Fighter created on a 3DS. Afterwards, turn on Custom Fighters and select the imported Mii. After that, select Mewtwo, and a "Random" option will exist under Mewtwo's default fighter.

Neutral Special 2
Mewtwo will charge an invisible Shadow Ball which will cause a burst of dark energy to hit every intractable object on the stage. This can cause a glitch known as Stage Morphing.