Andrew saw one of those games where you had to bash creatures that breifly popped up out of holes with a foam mallett; In this case, rats.
Deciding to have a go, he inserted some credit. Instantly the cartoon-like rats started popping up and down, but Andrew's reactions were fast and he splatted them more often than not. (the rats made a satisfying "OW!" sound when he hit them.)
Then the rats popped up and down faster and faster, and Andrew was barely able to keep up. He whacked them with the foam mallet more furiously, and ended up accidently hitting himself in the face with it! "OW!" he exclaimed, more out of suprise than pain.
The foam mallett hadn't given him any concussion, but the place did seem to be growing. What was more, he felt himself getting hairier - and something long and snakelike was growing out of his spine.
Andrew was turning into a rat!