On YTMND, users have created numerous alternate universes to YTMND, imagining how certain fads would look on a different website in a different universe. The most notable of these universes is PTKFGS (Punch The Keys, For God's Sake!).
These universes are usually distinguished with the YTMND icon. On YTMND, it's on the top-left corner. The top-right corner is widely accepted to belong to the universe of PTKFGS, while the bottom-right corner is widely accepted to belong to the YESYES universe. Any other universe using these spots are known as "Misc. Universes."
The 4th Corner is the bottom-left corner. Instead of one specific popular universe, the 4th corner is widely accepted to be a multiverse of more obscure universes, due to an explosion caused by Xenu.
Popular examples of some universes in the 4th corner multiverse.
It is worth noting that because the icon shares its place with the YTMND one, many of these aren't considered alternate universes.
Alternate Universes placed where PTKFGS should be.
Alternate Universes placed where YESYES should be.
Note that many of these aren't considered alternate universes due to the lack of an icon.