Both my cats are fixed, but I know that even fixed animals will sometimes still engage in sexual activity. But I’m not convinced that is what is happening here. It’s just WEIRD.
Cory (male) will stand over Ding (female) when she’s lying down, so that he’s straddling her, but standing up. He bites her on the back of the neck and then starts shifting his weight on his hind legs from one foot to the other. Sometimes he twitches his tail. Now there is a lot of air between them, he isn’t touching her at all except holding on to her neck, or even coming close to touching her. He also isn’t doing any humping/thrusting moves. Out of curiosity, I looked once and can confirm there was no kitty wiener sticking out, either.
So what is he doing? I assume it is some sort of dominance thing, though I don’t see the point–Ding is the most submissive, docile cat ever (except for being a’skeert of everything, everyone, and all sounds) and Cory is very mellow–not an aggressive cat.