"The Joker's disease" refers to a condition seen in the 2019 film "Joker," directed by Todd Phillips and starring Joaquin Phoenix. In the movie, the character Arthur Fleck, who becomes the Joker, suffers from a neurological disorder that causes uncontrollable laughter at inappropriate times. This condition is loosely based on real-life medical conditions such as pseudobulbar affect (PBA), which is characterized by episodes of sudden, uncontrollable, and inappropriate laughing or crying.

Pseudobulbar affect is often associated with neurological conditions or injuries, such as multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), or traumatic brain injury (TBI). It results from a disruption in the brain's pathways that control emotional expression. Treatment typically involves medication to help manage symptoms and reduce the frequency and severity of episodes.