- While enjoying teen-hearttrob success on The Hardy Boys, he released the single "Da Do Ron Ron," a 1977 cover of the Crystals' 1963 hit.
- His debut and sophomore albums sold more than 5 million copies.
- In an attempt to re-invent himself as a hard rocker, he teamed up with producer Todd Rundgren for his 1980 album, Wasp.
- Left showbiz altogether for several years in the 1980s to devote more time to his family.
- Starred alongside his brother David in the Broadway play Blood Brothers in 1993.
- Successfully launched a second career behind the scenes as a writer, creator and producer; his series include 1995's American Gothic and 2005's Invasion.
- Jack Cassidy — Father
- Ryan Cassidy — Brother
- David Cassidy — Half Brother
- Ann Pennington — Ex-wife
- Patrick Cassidy — Brother
- Shirley Jones — Mother
- Tracey Lynn Turner — Wife
- Susan Diol — Ex-wife
Ranking Big Bang Theory's Guest Stars
From Stan Lee to Leonard Nimoy, check out the greatest cameos on the CBS sitcom
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