He was often seen alongside The Fat Clown. The Thin Clown seems to be the a technician and specialist for the Circus Gang. He attempted a suicide mission once, running toward the Batman with a bomb strapped to his chest. He was promptly struck down and his bomb was stolen though (the Batman used it to blow up The Tattooed Strongman). Later, he and the Circus Gang hacked into the Batmobile in order to frame Batman for the ensuing damage.
In the Batman Returns video game for the SNES, there are four different versions of the Thin Clown: blue (common), tan (common), orange (juggles bowling pins), and green (carries a bomb).