Sounds to me like he is just playing
aggressively. That is a normal part of kitty socialization. If he had a playmate that is what they would be doing. I love L4's advice of getting a stuffed animal so he can take his aggression out on it. Or, better yet, her other suggestion of a playmate for him. As long as introductions are done properly if you decide to get another kitty they can play with each other and leave your arms and feet alone. A lot of kitty's play is just plain boredom. They need lots of toys, windows to watch out of, and attention from you if you are their only means of playing with another living thing.
Here's a video on bunny kicking. See if it's what your guy is doing.
- In a perfect world maybe
all vets would s/n at 4 months. But a lot of them are still opting for 6 months before doing the surgeries. The vets I use for that refuse before six months. Before that they say it is microscopic surgery. In some cases the males' testicles haven't even dropped until the fifth month. None of the kitties I've had done have been any the worse for waiting that long. JME