Sanford and Son (partially found spin-off series of NBC sitcom; 1972-1977)
Sanford and Son was a 1972-1977 series continued by three different spin-off show attempts, in which all three have lost episodes.
The first was called Grady where actor Whitman Mayo played his old man character of the same name as the series focused on his family. It lasted for 10 episodes during 1975-1976 and was canceled thereafter.
Episodes 1 and 2 have been uploaded on YouTube by user MYNEWCHANNEL-TOO, with episodes 3-10 yet to be found.
The second was called Sanford Arms made in 1977 starring Theodore Wilson as an old friend of Fred Sanford who bought the old house and rooming board from the original series in order to turn it into a hotel. The show ran for only four episodes after being cancelled with four others left being unaired.
Episodes #1-4 have been recently uploaded in parts by YouTube user Oliver Martin with the unaired 5-8 still missing.
The third was an revival of the original series simply called Sanford because actor Demond Wilson did not wish to reprise his role as Lamont Sanford while Red Foxx did as Fred. It lasted two seasons with 26 episodes. All have not yet been found online or released except for limited reruns on the BET Network.