A failed spin-off. The character, Richie Brockleman, appeared as a fellow PI helping Jim Rockford in "The House on Willis Avenue" (Season 4, Episode 21) of The Rockford Files.
Although the Richie Brockelman character had appeared in either two or four episodes of "The Rockford Files" ("The House on Willis Avenue" and "Never Send a Boy King to Do a Man's Job," which aired respectively in 1978 and 1979 as two-hour movies or two-part episodes), Dennis Dugan had actually introduced the Richie Brockelman character two years before in 1976 in the two-hour TV movie, "Richie Brockelman: The Missing 24 Hours." The five episodes of this series were telecast before either of the two "Rockford" two-part and/or two-hour episodes.
In the show, the character Richie Brockelman is 21 years old. The actor playing him, Dennis Dugan, was in fact around 32 years old by the time the show was aired.