dark
Explanation
The Joke
A child tells their father "Daddy, I'm afraid of the dark!" The father, rather than offering comfort, launches into a morbidly logical reassurance: "Don't worry. Eventually you'll be dead and you'll have no sense organs, nor any perceiving mind." He continues: "There's no darkness in a coffin. Darkness is a sensation experienced by a sapient being." He then stares at the child with vacant eyes and says "Vacant eyes see nothing, kiddo." The horrified child yells "Mom! He's doing it again!" and the mom calmly responds "It's okay! He'll be dead one day!"
The father is technically correct in a philosophical sense -- darkness requires a perceiver, and dead people cannot experience anything, including fear of the dark. But this is obviously a terrible way to comfort a frightened child, replacing one fear (the dark) with a much bigger existential terror (death and the void). The mother's response mirrors the father's logic perfectly: she comforts the child about the father's behavior by pointing out the father will also eventually die.
The Humor
The comedy works through escalation of inappropriate philosophical comfort. The father's response is a classic SMBC archetype: a character who is technically, philosophically correct but catastrophically wrong in terms of social and emotional appropriateness. The mother's punchline is the perfect capper -- instead of scolding the father, she has internalized the same nihilistic logic and applies it right back. The family is trapped in a recursive loop of morbid reassurance: every fear is "solved" by pointing to the inevitability of death, which should itself be terrifying but is delivered with cheerful matter-of-factness.