Aside from the always-hilarious violence, the characters in Thimble Theater were prone to be cowardly, deceptive, ugly, greedy, and heartless, but in a way that was somehow lovable, and very forgivably human. And somewhere in there lies a quality rare in any age, in any medium: that humanity. When the Sea Hag shows up, mysterious and barely visible in a sea of black ink, she is scary. When Popeye's latest sweetie (he and Olive were constantly switching up) says to him, "I DO NOT LOVE YOU," it hurts. This is not love and sadness, meanness and joy, heroism and hilarity approximated and packaged for you; this is the real thing. These characters' humanity has not been cleaned off of them by editors and PR agencies and focus groups: They are filthy with humanity—it hangs off them like a dirty old snotrag.
And maybe that's why Popeye is still around, 70-some years after the fact. He may have a cartoon heart, but it never stopped beating.