Spacefaring species whose ambassador's son, Tongo Rad, joined Dr. Sevrin's band of space hippies, complicating delicate relations with the Federation.
The Catullans were in sensitive negotiations with the Federation during Kirk's five-year mission. Because of that, Starfleet wanted any incident involving their ambassador's family handled gently.
In The Way to Eden, Tongo Rad, son of the Catullan ambassador, was among the followers of Dr. Sevrin who stole a cruiser and later the Enterprise itself in search of the mythical planet Eden. Kirk was ordered to treat the group with tolerance, and Tongo Rad survived the ordeal when the paradise they found proved deadly.