Starred on the Howdy Doody show. Quite a large clown, very typical with white face, red nose, etc. He was played by Bob Keeshan (who later became known as Captain Kangaroo). He would generally honk a horn to communicate (compare to Sideshow Bob and Sideshow Mel), and never spoke until the final episode when he said, "Goodbye, kids." And that was all.

According to some, one of the inspirations behind Krusty the clown was quite possibly Clarabell. Supposedly, in one particular episode of the filming of an episode, Clarabell had stepped off the set to smoke a cigarette and partially remove his costume to cool off. One young boy wandered up to him to see what was going on, and Clarabell is reported to have hissed at the child, "Get back, kid!" and sent the boy fleeing in terror. It took two security guards, Buffalo Bob Smith and the child's sisters to get him under control. So, according to this story, there's some speculation that the evil clown in Krusty (the part that hates kids, that is) was modelled after the differences in Clarabell's on-camera and off-camera demeanor.
References
Rusignola, Mike. Who was Krusty Modelled After? <http://www.silverbox.com/krusty/debate1.html>
Howdy Doody - Yesterdayland Saturday Morning Cartoons. <http://207.114.151.6/saturday/shows/synopsis/110.php>