RATHERstrange thing happened the other day, I had put some iron in my furnace and turned around to organize my chests, and got a small explosion in/on/next to my furnace, the only damage was 2-3 smooth stone blocks behind the furnace, the iron fence surrounding a chicken, said chicken and a chest next to the furnace, I also received 3 hearts of damage. I was playing on peaceful so Im 100% sure it wasn't a creeper. I had only been playing the game a few days and had no TNT. It end up happening two more times after putting iron ore into the furnace with similar results in the same furnace, I've since then tested it again in the same world and in creative W/O recreating the results. I did Google it and found another person W/ similar situation, but it was probably a creeper W/ him.
Well, in peaceful mode mobs spawn but disappear instantly. If a creeper spawned, it wouldn't have enough time to explode. Even if it did, you don't take any damage from mobs in peaceful. You also don't take damage from TNT either. In fact, you don't take damage from any explosion. So I bet it wasn't peaceful at all..
CREEPERSalso tend to do a ton of damage, and not just 2-3 blocks, and yes I do know they do less while on water, this was not on water. The game was on peaceful, there where no mobs no mods, and im not trolling... Can't post again today, guess there's a limit for new users. P: