My favorite was Pigpen. Sadly, Schulz stopped using Pigpen in the strip long before he died.
I actually met Charles Schulz at a writers' convention about ten years ago. He was polite and amusing, suffered from tremors (Parkinson's, I think), but still drew his strip himself, refusing always to let anyone else do it. He drew a big picture of Snoopy for a kind of door prize (I didn't win it).
He would hardly be the first humorist, in whatever medium, to suffer from depression, and have other detractive foibles. What matters now that he's dead is his work. Which is the way it should be.
Faulkner was a drunkard; Hemingway, too. Bertolt Brecht was, by all accounts, an absolute horror as a person. Ezra Pound was virulently anti-semitic, H. P. Lovecraft virulently racist.
The work remains.
caw