Very popular rock star of ancient Rome in the "Star for a Day" episode (23 Sep. 1972) of Hanna-Barbera animated series The Roman Holidays, an attempt to repeat their successful formula for The Jetsons and The Flintstones.
It didn't work.
Teen idol Cassius is sick and tired of all the attention and pressures of fame and wants a vacation, but he's booked at the Roman Coliseum. He runs into teen Happius Holiday (voiced by Stanley Livingston), who turns out to look just like him, when he puts on Cassius' wig.
Cassius' manager Max convinces Happius to take his place at the concert, lip-synching to a Davy Cassius record.
His name is a parody of real pop idol David Cassidy.