My boss asked me if I could work overtime.

This joke expertly employs a blend of irony and absurdity to land its punchline. The setup creates an expectation that the employee has a legitimate, perhaps even important, reason to consult their schedule before committing to extra work. However, the revelation that their pressing engagement involves "watching paint dry" completely subverts this expectation. The humor comes from the stark, exaggerated contrast (Review) between the implied busyness and the reality of an utterly mundane, time-killing activity, highlighting a profound disinterest in working overtime.

The humor also resonates with a common experience in the modern workplace. Many people can relate to the feeling of dread when asked to work beyond their contracted hours, often preferring even the most tedious personal activities to more time at the office. "Watching paint dry" is a universally understood idiom for extreme boredom, making it the perfect, comically understated excuse to convey a strong aversion to additional work without being overtly rude. It's a relatable fantasy for anyone who's ever felt the pull of the clock at the end of a long workday.