The Fused Shadow from Twilight Princess bears a striking similarity to Majora's Mask. It is highly possible that Majora's Mask was created by the same tribe who made the fused shadow, known as The Interlopers. This is made even more probable due to the fact that Twili are seen frequently wearing masks, as Zant and his Guard both wear masks, as well as the Shadow Beasts. In addition, when you steal the Ordon Shield from the village in Twilight Princess, Midna attempts to wear it on her face, like you would a mask.