I went to the doctor because I thought I was a pair of curtains.

This joke is a fantastic example of how a simple turn of phrase can transform a completely absurd situation into a genuinely funny punchline. The humor here primarily springs from wordplay, specifically a clever double entendre. The setup, with someone believing they are a pair of curtains, is wonderfully silly and immediately sets up an expectation for something ridiculous.

However, the punchline expertly pivots to a common English idiom: "pull myself together." This phrase is widely used to tell someone to calm down, regain composure, or get their act together, especially when they're feeling emotional or disorganized. The genius of the joke is that it takes this everyday expression and gives it a literal meaning that perfectly aligns with the initial, bizarre premise. Curtains, after all, are literally "pulled together" to close them. This unexpected literal interpretation of a familiar idiom is what makes the joke land so well, turning a nonsensical scenario into a moment of clever comedic clarity.