Joker (voiced by Mark Hamill) is Batman's arch enemy and a villain in Gotham City and one of the villains in Pooh's Adventures of Batman: Mask of the Phantasm. When the Joker discovered that the Phantasm who iced the old gang like Salvatore Valestra, Chuckie Sol and Buzz Bronski, he began to plan to kill the Phantasm and rule Gotham, but Batman and Pooh and his friends stopped Joker and saved Gotham.
Not much is known about how the Joker came to be, there are various origins as who he once was; each ending with him falling into a vad of chemicles, and coming out permanently dying his hair green and bleeching his skin white; thus giving him the appearance of a clown, and of course making him criminally insane.
- Joker came back with his girlfriend, Harley Quinn along with Two-Face and The Penguin to get revenge on Pooh and his friends in Winnie the Pooh Goes to Atlantis: The Lost Empire.
- Joker and Harley returned in Pooh's Adventures of Teenage Mutant Ninja Turtles and Pooh's Adventures of Teenage Mutant Ninja Turtles 2: The Secret of The Ooze where they worked with The Shredder.
- Joker and Harley appeared in the Bonus ending of Pooh's Adventures of Home on the Range.
- Joker and Harley recently returned in Pooh's Adventures of 101 Dalmatians where they worked with Cruella De Vil along with Jafar, Iago, Maleficent, Ursula, Hades, and The Grand Duke of Owls. They worked with her again in Pooh's Adventures of 101 Dalmatians: The Series.
- Joker and Harley will team up with Jafar, Iago, Maleficent, Myotismon, The Grand Duke of Owls, Captain Hook, Shere Khan, Kaa the Snake, Clayton, Scar, Shenzi, Banzai, Ed, King Ghidorah, Brer Fox, and Brer Bear to get their revenge on Pooh and their friends in the rest of Winnie the Pooh/Free Willy films.
- Joker will become the member with Two-Face, The Penguin, and The Fearsome Five as The Crime Empire.
- Joker will get his revenge on Ash and his friends in Ash's Adventures of Batman: Mask of the Phantasm.
- Joker will get his revenge on Littlefoot and his friends in Littlefoot's Adventures of Batman: Mask of the Phantasm.
- Joker will get his revenge on Simba, Timon, and Pumbaa and will become Bloom's enemy in Bloom's Adventures of Batman: Mask of the Phantasm.
- Joker, Harley, Two-Face, and Penguin will team up with the Ancient Minister and his family, Jafar, Iago, Maleficent, Myotismon, Ursula, Hades, Dr. Facilier, Scar, One-Eyed Sally, Blather, Captain Hook, Oogie Boogie, Icy, Darcy, Stormy, Team Rocket, and the Grand Duke of Owls to get revenge on Pooh, Ash, Bloom, Mickey Mouse, Simba, and their friends in Winnie the Pooh and The Halloween Tree.
- Joker and Harley will team up with Scar, Shenzi, Banzai, Ed, The Grand Duke of Owls, Jessie, James, and Meowth of Team Rocket to work for King Jareth in Ash Ketchum Goes to Labyrinth.