Night of the Axolotl

I had one of these when I was in school. They called it a "water dog" at the pet store. When it grew too big for my bed, I released it in the sewer. It grew and grew and ate a beauty queen, a pack of stoned teenagers, and the mayor before it was finally captured. The whole town was pretty angry with me. Luckily, they never traced that face-ripper demon back to me.