A dragon came, my first for my current DF gaming year (2014). While he spawned quite far to the west, I had forgotten that I had pastured some horses outside the walls near that side. The dragon proceeded to rush towards them before breathing out a breath fire that proceeded to generate a gigantic mass of fire that proceeded to spread out as it continuously burnt the lush green grass that was scattered all around my embark.
Then the dragon managed to get inside my walls, crossing the bridge connecting my fort to the outside world as I did not have any mechanisms in place yet. The inside was also ripe for burning so when the dragon let loose a breath of fire hotter than the sun, it had sparked a fire that proceeded to expand like the fire outside though at least most of my dwarves were in the statue garden located in the center of that place which had been floored off.
Miraculously, only two military dwarves died despite their severe lack of equipment (only one of my soldiers was equipped with any sort of armor and a decent weapon, the rest had only their clothing, a wooden shield and training weapons). The two that died dodged the dragon fire and fell in a murky pool beside the entrance, followed by the dragon who dodged the blows from the training weapons of my military dwarves. The oversized lizard then proceeded to tear apart the two though he was unable to kill the other one before he drowned.
Annoyingly, the initial breath of fire it used after getting inside the walls reached my depot which had contained my newly acquired leopard that was bought from the elves. Sadly, the leopard was was unable to escape his cage in time before the fire burnt its life to ashes. Oddly enough, the Stray Tigerman Herbalist and the Giant Lion which I bought along from those tree-huggers managed to escape from their burning cages though the lion is missing all the fat on its head.