When I was a kid in the 80s King John signed an autograph for me by balancing my autograph book on my head. I have pictures with him from our last trip in 2003 - maybe the Sherif of Nottingham too. They were in EPCOT.
Not regular, or even semi-regular at WDW or DLR. Last I heard they were out was when they did the "Long Lost Friends" event (maybe a couple years ago?).
I saw Robin Hood this past December at some outside dance party. Not sure if that is "Character Palooza" or not. They had a DJ with rotating characters that came out and danced with people.