In the early days of the WB they tried all sorts of cartoons in the 7-8pm hour before abandoning it all together on Sundays. The OBLONGS showed up on Sundays towards the end of the experiment (I believe they'd dropped 7-8 by then). The early 7-8 days were PINKY & THE BRAIN and other WB owned properties. I remember Superman, Batman, *AND* other shows. For a time the hour block of Pinky & The Brain was "remotely" successful. Once the WB found a place in the home of teenagers (and girls), they attempted to market as a niche channel.
Infant networks will try different things that premiere networks won't. UPN and WB picked up a slew of animated shows and paid for 13 episodes of each to be run. Both cell and claymation. Let's see: Gary & Mike, Dilbert, Baby Blues, Mission Hill, Home Movies, The PJs, and others were originally produced for them. About half would be acceptable for family viewing, but they were not kids-only intended.