While researching his Irish heritage, Jack Cassidy discovered his family's crest. He had gold pinky rings made bearing the crest, and gave them to his sons and his brother. His own ring helped authorities identify his remains after he was killed in a house fire.
Along with Stephen Boyd, Barbara Rush and Barbara Feldon, Jack Cassidy appeared in the 1973 ABC TV special Of Men and Women, which examined the relationships and differences between men and women.