According to some recently-surfaced concept art, Nintendo was once planning two games in the Zelda and Mario series with uncharacteristically dark tones.
ShineSparkers (opens in new tab) was the first to spot the concept art, which was apparently leaked by former Retro Studios concept artist Sammy Hall (opens in new tab). You'll see below that the images quickly circulated around Twitter.
Apparently leaked prototype art from multiple cancelled Retro Studios projects got leaked? The Sheik project looked STUNNING pic.twitter.com/3oUCwGJLx6May 5, 2020
Apparently, Nintendo recruited Retro Studios to develop a Zelda game that would follow the journey of the last Sheik after Ocarina of Time's "downfall timeline," where Link is defeated by Ganondorf. There are even fewer details about the Mario Boo project, but comments by Hall suggest it would've been a Nintendo DS game and feature possession powers akin to Mario Odyssey's Cappy. Both games were allegedly being developed during the Nintendo Wii era, and neither made it through pre-production.
The concept art for the Sheik game fits the grim mood of Hall's description well enough, with beasts that look even grittier than anything we saw in Twilight Princess. As for the Boo game, Hall seemed to be optioning a wide range of Boo variants, and some of them are pretty bizarre, like Hanukkah and Christmas Boo. You'll just have to see for yourself (opens in new tab).
I'm actually pretty bummed neither of these games ever made it to the finish line, because they both sound weird, dark, and creative in a way only Nintendo can pull off. The studio reportedly assigned to develop both projects, Retro Studios, is known for the Metro Prime and Donkey Kong Country series.
For now, at least we have Luigi's Mansion 3 (opens in new tab) for a spooky Nintendo fix.
For more news of the weird, here's Super Mario Odyssey "demade" into an N64 game (opens in new tab).