Roman said: I wanted to call seiyuu joke on this, but neither Bats or Vader is dueling Mark Hamill.
It's close. Mark Hamill voiced the Joker in the '90s Batman series. He's done the role a number of times, and is usually regarded as one of the best Jokers. I think it's the laugh.
Knowing Batman's penchant for researching his opponent and their weaknesses (particularly psychological) beforehand as preparation, he's probably lecturing Vader about proper parenting here.
