RTF is a global modification that replaces all towns in the game.

Awesome!

Added 7 minutes later
Well, it's easily explained... it happened like this... one very curious monkey (a breed very similar to nihon-zaru, or the Japanese macaque, by the way, an incredibly intelligent variety of the macaque genus) was transported through a portal by Ashi and ended up on an island where polar bears lived, and there were many lonely female bears. Well, somehow it turned out that sooner or later, nature took its course, and he had to please the lonely white bears... as a result, yetis appeared...