So I put together a collection of all the worlds that appeared there, and I can list a few:
1) The most obvious is the 'Paradise' mod, it's one of the most popular mods overall (an interesting fact I learned from Nerkin: the developer of this mod actually works at Mojang now lol, career ladder)
2) This is definitely not true, but the world that Blue and Red ended up in is very similar to the Infinite Tropics mod and the mod of the Most Annoying Minecraft (I don't remember the name, sorry)
3) At the moment when Purple and the Orange King ran by, there was an orange world; I'll guess it's the Beehive mod (when the apiary appeared, this mod came out almost immediately, but I know that's most likely not the case).
4) Backrooms lol
5) Minecraft, but the world is rotated 90 degrees
6) It's 100% certain that during these glitches, the guys weren't just running through mods, but literally through Minecraft versions, so seeing a world with a Ghast was not surprising
7) A world in a grid layout, where there’s only one block in each space (I remember watching Lololoshka's playthrough of this map)