Retro Studios is primarily known for its Metroid Prime series and two Donkey Kong games. And, according to some artwork of two canceled projects, it could have been known for Boo and Sheik games, too. These, of course, are the ghostly Mario enemy and the NPC from the The Legend of Zelda: Ocarina of Time.
ShineSparkers noticed this artwork for the canceled Boo game and Shiek title on Sammy Hall’s ArtStation page. Hall contributed to the art of Metroid Prime 3: Corruption as well as Donkey Kong Country Returns, two other Retro projects, lending credence that these ideas at least got to the concept stage. The Sheik game is under “Canceled Zelda project” from 2005 to 2008 and the Boo one is from “Canceled Boo project” from 2006 to 2007. The former coincides with a pair of NeoGaf rumors from around that time.
Given these timelines, the Sheik game likely would have been a Wii game. The scale for the artwork doesn’t point to it being something other than a console game. Hall describes this as a “long lost cancelled Zelda (Sheik) action/jrpg that never went beyond pre-production.” There are eight links and each of them have different artwork, but they have a strong look that are breathtaking and bold takes on the Zelda franchise. Some of these were posted years ago, but a couple of them were uploaded in the past few days.
The Boo title, however, looks like it was supposed to be a DS game, given how one of the pictures has “tiny stuff for tiny handheld resolutions” as its description. The more stylized art direction also points to a handheld release. Not much is known about this game, but it appears to take place in a Haunt University, which is further backed up by the cute Boo in a graduation cap. It also appears as though you could possess certain objects, which Nintendo has explored since then. You can see more of the artwork (including some that Nintendo probably didn’t like) here.