Shared Nightmares

Shared Nightmares is a phenomenon outside the realm of Super Mario 64 where many users claim to have nightmares of very similar topics. Much more attention was drawn to the idea of shared nightmares when anonymous users on 4chan shared their recollections of shockingly similar nightmares with one another that all related to Super Mario 64.

Despite the cheery and happy-go-lucky nature of the Super Mario series, Super Mario 64 is able to enstill a distinct level of unease in players that no other Mario game does. Whether it be the emptiness of the castle, the downright horrifying music in Big Boo's Haunt, or the negative emotional aura of Wet-Dry World, something about this game often makes people experience similar nightmares.

Kellogg's Penguins
In 1996, a limited time box of Kellogg's Frosted Mini-Wheats had a cross-promotion with Super Mario 64. On the box, unusual and unique renders of the penguins from Cool, Cool Mountain were used. The design used in these renders appears to be the beta design of the penguins, as seen in some early showings of the game.

These penguins disturbed many users on 4chan, with one anonymous user claiming to have had a nightmare where the penguins babble in an unintelligible language. Another user added that they had a similar nightmare, and warned other users to "wake up" if they ever have this nightmare, as 'they' (presumably the penguins) will hold the person captive in their nightmare.

Drowning Skeeters
While not as prevalent as Kellogg's Penguins, a somewhat sizable amount of players have reported having nightmares set in Wet-Dry World. The dreams consistently portray the water level continuously rising until the entire level is submerged. This leads to the Skeeters drowning, as they struggle before curling up and lifelessly drifting towards the bottom. These nightmares could be related to the Skeeter's 'Empathetic Emotional Aura' but this has not been confirmed.