grandfather-paradox
Explanation
This comic plays on the classic "grandfather paradox" of time travel. In the first panel, a man declares: "I don't think time travel is possible. If it were, I could go back in time and kill my own grandfather before he has kids, and I'd never exist." His companion simply responds: "Stupid."
In the second panel, the companion explains his objection -- but not for the logical reason you might expect. He says: "Well, your grandfather was a nice guy." In the third panel, his suggestion is even more unexpected: "I'm going for a philosophy professor you've never met." The final panel's caption reads: "While he's gone, let's get it on with Nana," showing two figures in silhouette with sinister intent.
The comic subverts the grandfather paradox thought experiment in multiple ways. The expected response would be a philosophical or physics-based objection -- something about causal loops or timeline consistency. Instead, the companion's objection is purely moral: he likes the grandfather and doesn't want him killed. His counter-suggestion to kill a random philosophy professor is both darkly funny and a dig at philosophy as a discipline. The final panel adds another twist: while the time traveler is away killing a philosophy professor, the companion plans to sleep with the time traveler's grandmother -- which itself would potentially create a different version of the paradox, since the time traveler might end up being his own grandfather (a nod to the plot of Futurama's "Roswell That Ends Well").