curses
Explanation
This is a single-panel comic with a caption underneath. The scene is entirely black (suggesting a dark bedroom), with two speech bubbles. Superman (referred to as "Clark") exclaims: "Curses! There must be kryptonite nearby!" His unseen partner responds wearily: "Clark, please." Superman then shouts: "Luthor! Show yourself!"
The caption below reads: "Late in life, Superman was unable to accept his erectile dysfunction."
The joke is a straightforward anatomical pun. Superman is experiencing erectile dysfunction — a common condition in aging men — but rather than accepting this as a natural part of aging, he blames it on kryptonite, the fictional mineral that weakens him and saps his powers. He even accuses his archenemy Lex Luthor of being responsible, imagining a supervillain plot rather than facing a mundane medical reality.
The humor works on several levels. First, there is the absurdity of applying superhero logic to an ordinary bedroom problem. Second, the joke plays on Superman's invulnerability — he is supposed to be immune to everything except kryptonite, so when something "doesn't work," kryptonite is literally the only explanation available within his worldview. Third, the partner's exhausted "Clark, please" implies this is not the first time this has happened, suggesting a recurring domestic argument. Finally, there is a deeper character comedy in the idea that Superman's identity is so wrapped up in being powerful and invincible that he psychologically cannot accept any form of physical failure, no matter how normal.