Explain SMBC — the wiki for Saturday Morning Breakfast Cereal

The Joke

The Joker confronts Batman, noting that they have been fighting for six straight hours and asking how Batman has never stopped to urinate. Batman calmly explains that his urethra is catheterized and he is constantly emitting a fine mist of urine.

The next panel shows a news headline: "JOKER SURRENDERS TO CAPED CRUSADER." The Joker is shown looking disturbed, clearly having given up not because he was defeated in combat, but because he was so disgusted by Batman's revelation.

The Humor

The comic takes the classic superhero trope of marathon fight sequences and asks a mundane, practical question that action narratives never address: when do superheroes go to the bathroom? Batman's answer is both horrifyingly logical and maximally revolting -- he has engineered a catheter solution that sprays urine mist during combat. The joke is that this biological detail is so repulsive that it accomplishes what years of crime-fighting could not: making the Joker simply quit. It is a parody of the "Batman is always prepared" trope, taken to an absurd and disgusting extreme.

References

• Batman and the Joker are iconic DC Comics characters. Batman is famous for having a gadget or contingency plan for every situation, which is parodied here.
• The "NEWZ net" headline panel parodies cable news coverage of superhero events.