10. Captain Clown
"You killed Captain Clown. You KILLED Captain Clown!"
Who can forget this hilarious outburst from Mark Hamill's The Joker in The Last Laugh?
Captain Clown is perhaps one of the most competent of The Joker's goons, for the perfectly good reason that it is revealed during the episode that Captain Clown is a robot - and a vicious one at that.
The captain is ostensibly meant to pilot a barge-load of trash, which The Joker has treated with his patented laughing toxin to bring Gotham City to a standstill so that he can loot the place silly, but Batman still battles Captain Clown several times. Almost every time, the robot easily bests Batman with its intimidating size and strength, before the Dark Knight finally hurls it into a garbage crusher. This enrages The Joker, who dumps a pale full of garbage on Batman in revenge. However, The Clown Prince of Crime soon forgets his woes and rides the captain's crushed remains on a conveyor belt deep into the bowels of his lair.
The presence of Captain Clown also sets up the presence of robots in Batman: The Animated Series, which would become key plot points in later episodes.