"Filbert E. Yarborough" joined Dave Hull's morning-drive show in December 1968 as sort of ajunior partner and straight man to the veteran comedic Hull.
"Yarborough" was really the new KRLA production director, Johnnie Darin, moving to KRLA from 136/KGB, San Diego.
The name "Filbert E. Yarborough" was an inside joke.
Darin had been working under the Bill Drake (real name: Phil Yarbrough) "Boss Radio" format at KGB.
Later in December 1968, Darin began using his "Johnnie Darin" name, dropping off Hull's show, doing fill-in work for Bob Dayton on the 3-7pm show.