A world I generated with a stream (The Weevil of Banks) that in many places has a "Haunted" biome on one side, and a "Mirthful" or similar on the other...

Extract to your "Dwarf Fortress\Data\Saves" folder.



[EDIT]: You can follow the stream in pretty much any direction for quite a way to get features you want, and still have the weird biomes. In fact, there are a couple placed where you can bypass the stream all-together and just get the two biomes, possibly with an aquifer or lake as a water source.