Concept art from Retro Studios recently found its way online and it depicted cancelled spin-off games based on both The Legend of Zelda and Mario franchises. IGN caught up with ex-Retro Studios concept artist Sammy Hall who produced the images and he explained that both the Shiek title and Boo from Mario were in pre-production phase and then canceled.
“I doubt many at Nintendo proper saw much of any of this stuff. I was mostly put into a room like Milton from Office Space and tasked to brainstorm between other projects.”Sammy Hall
“Zelda’s disguise in Ocarina of Time. It would have been an action-JRPG, set after the dark timeline of Ocarina of Time, in which the last male Sheikah travels across a ruined Hyrule while a Dark Gerudo tribe gives birth to a new form of Ganon. It would apparently have acted as an origin story for the Master Sword.”
“The other is a game based around playing as a Boo from the Mario series, possibly titled Haunt, and seemingly designed for a handheld consoles. It may have been set around a Boo learning to scare.”IGN
The actual idea for these games came from ex-Retro leads, Mark Pacini, Todd Keller and Kynan Pearson and the cancelation occurred as they moved to a new studio. However, it is likely that Retro terminated the project or alternatively was asked to explore other new ideas within established series, like Donkey Kong.