Jell-O doesn't wriggle, it jiggles! And I don't convulse -- well maybe just a few lady-like giggles!

No cachinnation? Only titters? Hmmm.... the latter evokes images of a feather-lined brassiere, which gets us back to what jiggles and doesn't wriggle. Oh - I see I've made your point! Ah, well, I'l never see Jello in the same light.