It's kind of amazing to me that there are two (2) long-running, syndicated, televised at least once, and merchandised comic strips about cats that... aren't actually about cats. 
You go on the internet and people are tweeting and tumbling about cats, sharing cat pictures and stories about their cats, it's this endlessly engrossing and highly relatable source of Good Content.
And then you open up The Funny Pages and cats are apparently all about I don't know, bubble gum and lasagna.
I mean, I guess Heathcliff also does strips about eating fish and knocking over garbage cans, there's plenty of absurdist non sequitur but also some clear nods to felinity. And Garfield... goes to the vet sometimes?
And to be fair Charles Schultz also used Snoopy for author insert stuff and elaborate fantasy scenarios, but there was also stuff about being a dog (SUPPER TIME!, fighting with the cat next door, etc.) and the whole strip wasn't about this dog who sleeps on top of a TARDIS.
And with Snoopy, the absurdist stuff and the dog who thinks he's a person (and Peppermint Patty sometimes mistaking him for one) is all fodder for in-universe humor, too.
But so much of Heathcliff and Garfield are just like... like the opposite of that Nathan Pyle strip where aliens describe familiar earth experiences in banal sci-fi expospeak.
"Haha. That cat hates Mondays. Don't talk to him before he has coffee."
"Haha. That cat hates Mondays. Don't talk to him before he has coffee."
Meanwhile, actual cat humor is amazing.
