Abramovici Twins

The Abramovici Twins appear in Batman: Arkham City.

Before Arkham City
The Joker saw the Russian conjoined twins performing in a circus and decided he wanted them to work for him. He sent Harley Quinn to offer the Circus owner money for them but he refused, not wanting to lose his headlining act. He vanished for a while after this, turning up weeks later with a permanent smile cut onto his face.

Mister Hammer

 * Main article: Mister Hammer

Sickle

 * Main article: Sickle