pun-tourette39s
Explanation
The Joke
The comic's header declares: "The hardest psychological disorder is Pun-Tourette's." A woman is telling a tragic, serious story: "And then the wild dogs came. They were starving too. First they came for the children, for they were weak with hunger." A man in the audience involuntarily blurts out: "That sounds... RUFF. I am so sorry."
The man suffers from "Pun-Tourette's" -- a fictional condition where he cannot stop himself from making puns, even during the most inappropriate and tragic moments. "Ruff" is both a word meaning rough/difficult and the onomatopoeia for a dog's bark, making it an involuntary pun on the story about wild dogs.
The Humor
The humor operates on multiple levels. The core joke is the concept of "Pun-Tourette's" itself -- imagining a condition where someone is compelled to make puns at the worst possible time. The specific pun ("ruff" during a story about wild dogs attacking children) is deliberately terrible, which is part of the joke: it's not even a good pun, making the compulsion even more pathetic and embarrassing. The man's immediate, anguished apology ("I am so sorry") sells the idea that he truly cannot help himself and is mortified by his own behavior. The comic also plays on the real-world experience of people who are habitual punsters and seem unable to resist making puns even in serious contexts.
References
Tourette syndrome is a real neurological disorder characterized by involuntary repetitive movements and vocalizations called tics. The popular (though medically inaccurate) stereotype of Tourette's involves involuntary swearing (coprolalia), which the comic repurposes as involuntary punning.