Big Boo's Castle

Big Boo's Castle is the conjectural name given to a supposed early version of Big Boo's Haunt from the final version of Super Mario 64, as it seems to not really have an official name. General descriptions of the level seem to suggest that the level itself contains an altered version of Princess Peach's Castle instead of a mansion.

Description
Based on the reports provided below, if they are true, Big Boo's Castle seems to look similar to Big Boo's Haunt, but with the mansion being replaced with a castle like Peach's, how altered it might be is unknown. The Merry-Go-Round area is also not mentioned by these reports, so it is either assumed to be the same as the final area, or that the area itself wasn't around at that time. Boos seem to be an abundant enemy in the game, with lots of them seeming to appear in the castle and its outskirts.

Reported Sightings
Anything from this section should be taken with skepticism, as these claims seem to be unverified

Report #1
Report #1 of Big Boo's Castle was found on a now-defunct Geocities website regarding obscure facts and rumors about Super Mario games. The facts seemed to be ordered in a list, with Report #1 being the fifth fact on the sight. The website had stated this as it follows:

Fact # 5 - Big Boo's Castle

''Big Boo's Haunt was spooky on it's own right with ghosts, eyeballs, books, and pianos on the hunt for our portly plumber. Hearing about a second area in the game that contains more haunting sightings is off-the-wall! That's right, it is rumored that there's another version of the area that contains a castle similar to that of Princess Peach's, albeit with scares and haunts to frighten Mario. As such, this area was dubbed as Big Boo's Castle.''

''The only known star of this secret area is known as "HUNT IN THE BLACK VOID" in the level select screen where normally Big Boo's Haunt is supposed to be. Of course, considering that its the only known star of this level as of now, it's most likely impossible to get due to no "black void" being around. The only thing that's there is of course, Big Boo's Castle. Only Boos lie in this decrepit fortress, as far as it has been known. Who knows what lies ahead of this secret area, or how we can seem to find it clearly. Maybe this is how you can unlock Luigi, considering that he's naturally afraid of ghosts.''

Report #2
This report of Big Boo's Castle was found in a forum for gaming discussion, with the title post on the thread that contains it being titled "Help: Trying to find a star in Super Mario 64". It seemed to be flamed down because of skepticism, meaning that this report could have been dated much earlier than other reports of personalisation. The thread goes as follows:

Everrot39 says:

''Okay, has anybody ever had trouble finding this star in Super Mario 64? It's in Big Boo's Haunt, the area that has a castle in it, much like the starting area of the game. The title of the star seems to suggest that I should defeat some sort of "black void", but I can't really seem to find it. Maybe it has something to do with falling out of the gates bordering the area? I don't know where to find anything regarding that.''

DamienIsTheBoss says:

''I'm not sure if this is trolling or if you are serious, but if the latter's the case, are you playing a hack of some sort? There's no castle in Big Boo's Haunt and none of this "black void" of some kind in the game.''

ChickenWarrior2 says:

''OP is definitely trolling. No way would this be the only time we heard about this "castle" in Big Boo's Haunt. Gotta say, that's a shitty trolling effort. Try harder next time.''

Everrot39 says:

''I'm not trolling! There is a castle in my game in Big Boo's Haunt! I know there's somebody out there who has this in their game.''

98DollarsAndCounting says:

''I don't think that Everrot's alone on this one. I think I know what he is talking about, and I am probably stuck on this one too. Maybe use a Gameshark if you can't find a way to find the black void as a ditch effort? It's what I did. I don't really remember that much after that. Its probably either a boss fight with some sort of black mass or a platforming area outside the cage. I could only remember a few parts of it well, it has been a while since I played Super Mario 64, and the original copy I have seemed to be gone. The new one I got doesn't seem to have this castle. Also, I think the title was something among the lines of "Hunting in the Black Void" or something like that.''

ChickenWarrior2 says:

''lmao look at Everrot using a sock account. This is comedy gold right here.''

DamienIsTheBoss says:

''Ok, now I think you're pulling my leg. How come I never got to see this "castle"? Although to my knowledge, my copy of the game seems to be a bit off, so I probably am a bit of a hypocrite. Those "100-coin stars" seem to be collectible after what I think could be around 60-80 coins iirc.''

ChickenWarrior2 says:

''I can't believe you're egging Everrot on! It's obvious that he's full of shit. There is no castle. You guys are a riot!''

ModRaven says:

''Closing this thread. It's probably a trolling effort, and I don't think we have time to natter about "spooky haunted" copies. Take that to the Creepypasta Wiki.''

Theories
One theory regarding Big Boo's Castle would be that the castle itself was a placeholder for the mansion, and the area itself was an early version of Big Boo's Haunt. There seems to be no reports on other areas like the Merry-Go Round area under the mansion, so it could be a very early version of the level. How it got there is most likely due to the Personalisation A.I bringing in the area, replacing Big Boo's Haunt.