I want to add a couple of good ones I’ve found:
Jeff the Killer lost media: no one knows where the original Jeff The Killer image came from.
Mortis.com: old weird website
Also here’s a good website on various obscure computer/Internet related oddities: https://suricrasia.online/iceberg/
There might still be the “Twitter numbers” accounts that post some set of numbers or words at specific times.
Basically it’s just the internet version of the “radio numbers” or “radio codes” that are radio signals that randomly or schedule voice a set of numbers or words. There go back decades.
The theory is that it’s a commutation network for spies.