I've been making a homemade bird food mix for a few years. The base starts with 1 cup of lard and 1 cup of peanut butter. I place them in a 2 quart Pyrex measuring cup and nuke them for 2 minutes. I had just a little bit more left in the Peanut Butter container before it was empty so I added it to the Pyrex cup and set the microwave for 2 minutes and 15 seconds. I noticed what looked like a flame in the microwave and quickly shut it off, with 42 seconds of cooking left.

Warning - Please Read!
http://www.eurekalert.org/pub_releases/2012-09/tacs-np091112.php

I put the cup on my counter and added 1/3 cup of sugar to it. A few seconds later I heard a crack and this is the result. I have never had a worse mess to clean up, except for the quarter jar of duck sauce I once dropped form the fridge.

From now on the lard and peanut butter will be melted on the stove!

(The rest of the ingredients are flour, oatmeal, and cornmeal)

Warning: http://housewares.about.com/od/bakewareservingware/qt/Glass-Bakeware-Safety-Tips.htm