garfield
Explanation
The comic reimagines the Garfield comic strip with a dark, realistic twist. In the first panel, Jon cheerfully announces: "Garfield! I made your favorite -- lasagna!" In the second panel, Garfield responds from his bed: "Jon. Jon, I was born in 1978. No cat has ever lived more than 40 years. Jon, I'm gone. Long gone. You know this."
In the third panel, Jon, still smiling, says: "Sounds like someone's having another terrible Monday!" The fourth panel reveals what's actually in Garfield's bed: a cat skeleton under the covers.
The comic takes two signature elements of Garfield -- the cat's love of lasagna and hatred of Mondays -- and recontextualizes them through the lens of actual feline biology. Garfield the comic strip began in 1978, and in real life, no domestic cat lives to be 45+ years old. The comic forces the reader to confront what would actually happen if Garfield were a real cat: he would have died decades ago. The horror of the final panel -- revealing a skeleton where Garfield should be -- is amplified by Jon's cheerful obliviousness. He's still bringing lasagna and interpreting the silence as Garfield being grumpy about Mondays, suggesting Jon has been in denial about his cat's death for years, possibly decades.
This is a well-worn genre of "dark Garfield" humor (see also Garfield Minus Garfield, and various "Jon is hallucinating" theories), but SMBC's version is particularly effective because it uses Garfield's own internal monologue as the vehicle for the reveal. Garfield himself is the one who breaks the fourth wall to explain that he's dead, making the final skeleton panel hit even harder -- the voice we just heard cannot possibly be coming from that bed.