best-3
Explanation
Two people discuss: "How do you think the world's best day will go?" One says "I dunno." The other explains that they are a "best-day-ever futurist" and argues that if you believe there is one specific time and place in all of history that is the best day ever, then everyone will want to visit those exact spacetime coordinates. The implication is that if time travel exists, the "best day ever" location would become so crowded that it could not possibly be enjoyable. Furthermore, the sheer gravitational and physical impact of everyone in history converging on one point could be "so vast that it causes the end of the universe, pulling the fabric of reality into the singularity from which the best day ever began." The first person notes "free non-catered lunches" would be available at the end of the world, prompting the futurist to remember they have "reserved a table at the end -- man, the nachos never die."
The comic takes the concept of "the best day ever" and applies absurd logical rigor to it, treating it like a physics thought experiment. The joke builds through several layers: first, the silly premise of being a "best-day-ever futurist" as a career; then the time-travel paradox where the best day becomes the worst day because of overcrowding (similar to Yogi Berra's famous quip "nobody goes there anymore, it's too crowded"); and finally the cosmological catastrophe of all matter converging on a single point creating a singularity. The punchline shifts to mundane concerns about lunch reservations at the apocalypse, deflating the cosmic scale back to everyday triviality -- a classic SMBC technique of combining grand physics concepts with petty human concerns.