Unlike the other posts I can see this one happening. There is a possibility.

There is a possibility that tensing up your shoulders, then your hands that way is a really weird stim. I find tensing up my body (squeezing hands, curling toes, digging hands into clothes) a good way to fulfill that need. Many of my stims are closed-in kind of actions like that where they are tense.

Laughing like a maniacal villain? If you are so happy that it’s hard to contain and you want to laugh it out, that’s something I do. The evil villain part is probably some internal quirky joker arc which probably gave off the impression of faking. The two line up because of that in an attention-seeking ‘yeah, sure, cool’ kind of way, but I think there’s a chance they have autism.