The Quetzalcoatl was a feathered serpent that was terrorizing the streets of Mexico in it's endless hunt for food.
The Somewhat Pointless Adventures of Zippy Edit
The Quetzalcoatl was discovered by Zippy and Mulder when it was reported to be running through the streets of Mexico and killing anyone that came in it's way. Zippy and Mulder hunted it down and eventually managing to lure it out using Zippy as bait. It got it's tooth trapped in the zip on Zippy's mouth and was unable to set it's tooth free. This made it vulnerable as it could not move Zippy due to the fact that he had been weighted down to the ground using very heavy objects. Mulder intended to merely render it unconscious but was forced to kill it when Zippy's life was put in danger.