Dan was stunned by the sheer size and strength of the appendage that had grown out from him. His pants had been no match for it. He could feel it dangling on the ground and extending for quite some distance behind him. It was covered and short fur, and it was thick with sturdy bone and flesh. He couldn't believe that all of this had grown in so quickly, and he was quite disoriented from suddenly feeling so much of the floor behind him while standing up.
When he was less dizzy and had made a bit more sense of what he was seeing and feeling, Dan came to the realization that his tail was just as strong as it looked: it was like having a whole other pair of legs behind him! He could rest the full weight of his body back on the tail as though it were a chair he could sit in. In fact, he could even kick his legs up in front of him, using the tail as a pivot. It was actually kind of cool in its own way, but he also had to face the realization that Kat can do just what she promised to do to him.
"I'm really going to be an animal?" he said to himself. Apparently, over the next few hours or days, he was going to turn totally into an animal with a very long thick tail.
"I look like a kangaroo already," he though, looking back again at his tail. In less than a week, or even less than a day, he might very well be one.