I was sitting at my desk - reading the morning or evening Internets, respectively - with Huckleberry sprawled across my chest, as is often the case at such times.
It was time to stand up. I started to do so... and my elbow rest (one of those fabric-covered-foam wrist rests, only for my left elbow) apparently stuck to my elbow and moved with it.
Huckleberry freaked out, and launched himself in any convenient direction at maximum boost, leaving scratch marks behind on various portions of my anatomy.
In the morning, he went to my right, landing in the wastebasket.
In the evening, he went almost straight up, landing behind my chair.
So I showed him the elbow rest, and explained to him that it was inanimate and harmless.
Then I tied a felt-feathers-and-jingly-ball toy to the dangling ribbon of a leftover birthday balloon, such that it was within leaping range when the balloon was on the ceiling. He's been having fun chasing it around, in a place where I'm not.
Update: Unable to duplicate problem. The elbow rest obstinately refuses to follow my elbow around, with or without a pajama sleeve. I must conclude, therefore, that Huckleberry had been resting his paw on the elbow rest, claws extended, and the scary object moved because he had a claw snagged in the covering.