I have this imitation I do at parties. Most of my friends have seen me do it several times but it's pretty funny and they'll say things like "You should watch him do this" or "Check this out; it's pretty funny" to the person they're talking to. Sometimes they will prod me and say "Come on, Robert, do that thing" and I'll hold my hands near my face and say "Oh, no. Not at a party" and then I'll do it.
It's pretty subtle, mostly gesture and expression, and a lot depends on lifting an eyebrow at precisely the right moment or on the way I curl my hand around my glass or can of beer or whatever and point my index finger just so. It's more like a gestalt or a channeling or something psychic than just doing an imitation, an impersonation.
A girl I met at a party asked me to do it for her the next morning. She said, "Do that again. Do that thing you did at the party."
I pretended to have no idea what she was talking about.