When I was living in my first off-campus apartment, I discovered two things:
1) I really enjoyed baking cookies and
2) My roommates were not to be trusted with an oven. At all. The number of times I came home just in time to rescue plastic plates and takeout containers that were being heated for "just a few minutes"...
So one night I was making my favorite oatmeal raisin cookies, just for fun, but I decided that the dough needed to chill longer (I start with melted butter, makes for chewier cookies) and that I would just wake up at 6am and bake before going to campus.
Well, what I didn't realize was when my roommate had sworn she had cleaned the oven (from a previous plastic incident), what she meant was that she had not, in fact, cleaned the oven. But I, merrily oblivious to this fact, turned on the oven to preheat and started shaping the first batch. So when the fire alarms went off, I thought to myself, "Huh. How annoying. I better turn those off." (In my defense, they did tend to go off every time anyone cooked anything).
Cut to me opening the oven, cookie sheet in hand, only to reveal a happy little flame at the back of my oven. And I can only blame my gut reaction on the fact that it was 6am: "if I put that out, can I still bake my cookies?"
I ended up filling a frying pan with water, dousing the oven, and then calling Maitenance to inquire about the box full of flame in my kitchen. And needless to say, from that point on, I made sure to clean the oven myself.