Joker

Clown Prince of Crime

Jack Napier
The Joker

Human

Gotham City, USA, Earth

Jeannie (Estranged Wife)
Harley Quinn (Partner)

Jeremy (Son)

Failed stand-up comedian, mentally imbalanced homicidal maniac
Began his criminal career as "Red Hood", Fell into a vat of acid while fighting Batman;
Survived, skin turned pale white & his hair green, permanent smile on his face
Terrorized Gotham City, sent to Arkham Asylum, when caught by Batman
Killed Jason Todd & paralyzed Barbara Gordon by shooting her in the back

Legion of Doom

Cesar Romero (Batman 1966)
Mark Hamill (Batman TAS)
Jack Nicholson (Batman 1989)
Heath Ledger (The Dark Knight)