He was active in the late 60s and 70s. Moon face, dark curly hair, big walrus mustache.
I remember the routine he did with another guy where he was an automaton on a subway platform who would talk and give advice for coins, usually stopping mid-sentence to encourage the mark to put in another coin.
Well lucky that came up because I might have forgotten I was old. I didn’t think of the Muppet Show, assumed they were Rowan&Martin guests like someone else did, but I was sure Mummenschanz hadn’t been on the that.