IIRC, Jim Nabors’ character had been quite popular and, when he left to do Gomer Pyle, USMC, the producers introduced his cousin as a replacement.
Yes, I remember that. When Gomer left, I didn’t think his replacement would be able to do well at all.
After a few episodes, I liked Goober better.
Shortly before Jim Nabors left The Andy Griffith Show to do his own show, there was an episode in which Gomer and Goober walk into the Court House, where Gomer introduces his cousin Goober to Andy. Gomer then prods Goober into doing his famous Cary Grant impersonation for Andy - "Judy, Judy, Judy!" (Of course, he didn't sound anything like Cary Grant.) I believe this is the only episode in which Gomer and Goober appeared together.
The character of Goober preceded Gomer’s departure for the army.