I had to scratch my head at those various characters being referred to as obscure, since I recognized every last one of them. Maybe it's just that Snagglepuss wasn't around as much as Huckleberry Hound, but come on, the two of them and Quickdraw and Oggy Doggy (and Doggy Daddy, my son, my son) went on pretty much every crossover adventure Yogi had.
It could also be that I watched the Laff-a-Lympics religiously as a child, so after a few years of that, I'm intimately familiar with Hong-Kong Fooey and Captain Caveman and Jabberjaw and all the rest. But I also remember seeing reruns of their individual shows, so I dunno.
People who want a real nostalgia trip on HB properties need (desperately!) to watch Harvey Birdman: Attorney at Law. Not only is the titular character an old HB mainstay Birdman, but nearly all of his clients and supporting characters are from the HB universe, including Inch-High Private Eye, Magilla Gorilla, and Blue Falcon/Dinomutt, as his Latin nemesis, Azul Falcone.
Here's a classic example: Grape Ape caught 'roiding up at the Laff-a-Lympics:
http://video.adultswim.com/harvey-birdman-attorney-at-law/grape-ape-competes.html