[Rinni]

I play on a friend's private server, and I have two single player worlds I play in.

In one, I spawned in the tundra. Thought "Okay, cool!" and built a house. In my backyard, I found there was a random hole in the ground with lava in it. Found it by falling in. XD And, a bit further back, there's a canyon with water and lava falls. Built a tunnel to it.

In the other, I spawned in an NPC village. Decided to build more houses. Didn't realize that doors made them reproduce like freaking rabbits. To give you an idea of how many villagers we had.... I had 12 naturally spawned iron golem in the village. @.@