I always had an interest in the SCP Foundation while hating the titular foundation itself for its crimes against nature and humanity, but when it comes to personal favorites, I often have a hard time picking between Backrooms and Easter Egg: Snow on Mt. Silver because both are interesting concepts.
For as flawed as Snow on Mt. Silver is, I like the concept of a Pokémon Gold or Silver cartridge hiding something sinister in it as unrealistic as it is. After all, the whole point is that the permanent death feature and disturbing content were supposed to be hidden on all copies of the game which, if that were true, the Pokémon franchise would never survive the controversy that would come after getting a bunch of complaints from angry parents and traumatized kids. That would mean the series would be cancelled with no chance of sequels; no Ruby or Sapphire, no Diamond or Pearl, nothing. Apparently it also got a sequel called I'm So Hungry which kind of retcons everything. I came up with the idea to rewrite it and changed the haunted cartridge into a haunted ROM hack found on some shady GeoCities-esque website that masquerades as a rebuild of the Space World prototype. I called it "Project Fuji".
For the Backrooms, I actually gained so much intrigue in the concept of a parallel universe occupied solely by liminal spaces that all started from that infamous photo of an empty furniture store, that I made a graphic novel about it called Blood Hounds, although only the prologue is available to read online since the real first chapter is still in the works.