Believe it or not, there was actually a time when the USA network showed something besides Law and Order reruns. Once upon a time, there was a block known as Cartoon Express. I spent many Sunday mornings watching old Hanna-Barbera cartoons (though I usually ignored the weekday afternoon block). Cartoon Express produced possibly some of the best bumpers ever.
Here's a bumper featuring Slimer from The Real Ghostbusters:
Here's one featuring a bunch of Hanna-Barbera characters: