I remember Captain Caveman and Birdman, the latter somewhat more clearly than the former. I remember thinking Birdman was cool, which is odd because I always thought Space Ghost was kind of lame. I never really recognized any similarities between the two, though I'm sure if I went back and watched them both now it would be obvious. H-B reused a lot of stuff. How many freakin' rehashes of Scooby-Doo did we have? Speed Buggy, Josie and the *****cats, Funky Phantom, some other ones I'm probably forgetting were among them. They weren't exactly the same, mind, but most of the same character archetypes were present in each, and I know for a fact that the Shaggy-like character in Speed Buggy wore a green shirt and looked and sounded quite similar. I also know that something like half a dozen JatP plots were reworked S-D ones.
Now I'm not knocking H-B. They were a big part of my childhood, and I'll always treasure the memories of the time when all the stuff in the above paragraph never occurred to me and wouldn't have even bothered me if it did. It's kind of sad, actually, that now that I'm older a lot of the classic H-B stuff can't really entrance me the way it did when I was seven. This growing up thing is overrated, IMO.