My cats are nuts- and yours?

Does anyone else's cats have spasms? I mean sudden millisecond entire body flings into the air from a standard sitting or walking position- and then everything is fine again.
How about the I-just-pooped full throttle laps? Do they feel that much lighter and freer, or are they running from the hideous smell?
I used to laugh hearing my neighbor yell at her cat- I felt like part of a club.
"Get down!" she'd boom. I was pretty sure it wasn't her husband up on the counter.