I wish Mark Hamill all the best in future roles. 18 years of voicing the Joker, obviously three times longer than playing Luke Skywalker in the Star Wars trilogy, is very hard to argue with, but nonetheless, there are a lot of memories of him as the Joker. I remember watching Entertainment Tonight, back in 1993, where Mark was discussing playing the Joker in Batman: Mask of the Phantasm, at which he also spoke about frightening some motorists on a local Los Angeles freeway while practicing his Joker laugh. I would assume that one motorist probably thought, "Oh my gosh, that Joker laugh is coming from Luke Skywalker!" Playing the role of the Joker for 18 years, aside from playing Luke Skywalker, would have to be the role of a lifetime for Mark Hamill, and whomever succeeds him in that role won't quite have the same charisma as Mark. At the end, he'll probably say, "Hey, Batsy, catch me if you can", then finish off that line with a maniacial laugh, but that's how Mark Hamill portrayed the Joker.