mucus
Explanation
The Joke
An elderly man sitting in a chair tells his grandchild about a prolonged disease he survived, explaining that he got "very comfortable talking about body stuff" because there are so many shades of mucus, and "where it really gets gross is—" The grandchild pleads: "Please, no more, grandfather." The caption reads: "Whatever doesn't kill you makes you stranger."
The Humor
The comic subverts the inspirational saying "whatever doesn't kill you makes you stronger" by replacing "stronger" with "stranger." The grandfather survived a serious illness, which is typically framed as a story of resilience and strength. Instead, the lasting effect is that he now has zero filter when discussing bodily fluids — he's become a mucus connoisseur who can't stop sharing his expertise. The grandchild's discomfort mirrors the audience's realization that surviving hardship doesn't always produce wisdom or strength; sometimes it just makes people weird in very specific ways.
Broader Context
SMBC often takes aim at inspirational platitudes and shows what they actually look like in practice. The Nietzsche-derived "what doesn't kill you makes you stronger" is a frequent target in comedy, but Weinersmith's version is distinctive because it's not just contradicting the saying — it's offering a more accurate alternative. Prolonged illness really does change people in unexpected ways, and those changes aren't always noble or inspirational. The comic fits into SMBC's broader project of replacing comforting generalizations with more honest (and funnier) specific observations.