Newly-released sandbox adventure game Hytale originated as a Minecraft mod, Hypixel, only to eventually be spun off and transformed into the early access, standalone game we now know. But even so, I don't think anyone had "Minecraft x Hytale crossplay" on their Bingo card.
This wizardry comes from modder u/ssquadteam, also known as iamcxv7, a 15-year-old modder who has also managed to get things like Windows 95 running in Hytale and, separate from the guy who did it pre-launch, Doom. iamcxv7 has managed to figure out how to get Hytale and Minecraft to talk to one another so that players in one can play alongside players in the other, seeing one another's characters rendered in their own game's style, interact, build, chat, and even...