Mushroom from Hell?

Ok, last Sunday morning I woke up to see what I thought was a cat sitting in the backyard. That is not too odd as there are a number of cats that wander into my yard to eat the wildlife around the house. However, I noticed that this one was not moving, so I decided to go out and investigate. What I found was a GIANT mushroom that had formed over night. Check out the pics at flicker.