My clearest recollection (don't know the episode) is when he attends an event, probably in place of Alan Brady, that turns out to be a big fund-raiser. The Hostess addresses him as Mister Petrov. When asked for a donation, he is stupefied, and can only say "I have this blank check" ... no spoiler ...
The comedy show within a comedy show is a cool dramatic and operatic trick.
Magnificent delivery.