From The Andy Griffith Show:
The Darling family (Denver Pyle, Maggie Peterson, and the bluegrass group, the Dillards) are in jail, but Sheriff Andy Taylor (Griffith) joins them for an impromptu jam. Charlene (Peterson) sings lead on "Salty Dog", with the family band aided by Andy on guitar.
16 years later, Pyle would play another backwoods father figure in Jesse Duke on Dukes of Hazzard, but never sat in with any of the musical guests on the show. Then again, co-stars John Schneider & Tom Wopat never used the show to further their budding musical careers, either.