Gonna just go ahead and mirror the contents of that main post here in case it disappears...
"I found these images while researching the Super Mario Puppet Kooler. It shocked me when I saw beta images and I knew I had to upload them here!
The title screen
Sadly, no link to the original source of the images on the page, but reverse searching the title screen image brought me to this page, which appears to be the original source:
" "BUBSY" PROTOTYPE (Title screen image above shown to right)
There's actually a version of Bubsy out there LESS polished than the original
When sticking it into your system, you may want to be careful(text here linked to image of the board)
eBay Price: $799.00"
There is sadly no implication that the owner of the page owns any of the items shown, including the Bubsy prototype, and as it states the eBay price, that must be where they grabbed the images from... sadly, that listing is probably long gone now, and was never archived, so unless a dump circulates or the proto is sold again, you may not find out any more than now... the price was wild, too.
Might be still worth contacting the owner of the page, though!
The only other place that seems to show the same image is this page, but doesn't really mention it. It talks about other "rare" Bubsy stuff, though, if you're into that. The owner of that page seems really into Bubsy, so they might have more info for you?
I've tried tracking this down and haven't had any luck. The image metadata seems to suggest the pictures are from April 2012, so going with that I did some searching here and there and found a couple old Bubsy proto auctions going back that year, but eBay doesn't archive the winning bidder names so I can't see who won. Pretty sure neither cart was this one, though, since both I found were open auctions that ended just over $100, whereas this one apparently was listed with a BIN of $799.
Really puts into perspective how things on eBay end up lost to time. Assuming this never sold, the seller just gave up and maybe stashed it away for no one to ever inquire about again.