Role in the series
Originally her servant, Kaj became tired of living as La's slave possibly many years after being turned from a leopard into a Leopard Man and instigated a rebellion in which he stole Queen La's staff before dethroning her. Afterwards, he had his fellow Leopard Men kidnap Jane Porter, hoping that by crowning her as Opar's new queen, she would free them from the spell La had placed on on them. However, kidnapping Jane brought the ire of Tarzan, who was tricked by La into retrieving Jane before Kaj could could complete the ritual. After Tarzan and La defeated them and the former left with Jane, La intended to teach her Leopard Men to fear her by sacrificing Kaj to the giant octopus she kept in the dungeons beneath her palace. However, Tarzan, Jane, Terk, Tantor and Professor Porter returned to save Kaj after Jane explained the Leopard Men's plight. Tarzan saved Kaj as the octopus tried to drag him to his death, only to be grabbed himself and pulled into the depths. Forlorn at the loss of Tarzan, he revealed Tarzan's "death" to Jane, allowing Tarzan (who had escaped the octopus) to steal La's staff and give it to the former. Jane then reversed the spell, killing La's body in the process and returned the Leopard Men, Kaj included, to their natural forms: leopards.
In his Leopard Man form, Kaj is defined from other Leopard Men by his green clothes.