Ernie's muscles are not paralyzed when he is dreaming. As a result, he literally acts out his dreams, sometimes injuring himself in the process. Ernie appears to suffer from:

Ernie appears to suffer from: Rapid eye movement (REM) behavior disorder.

Rapid eye movement (REM) behavior disorder is a sleep disorder in which an individual act out his dreams, followed by disturbing dreams with sounds and vicious movements of the arm and leg during sleep. REM behavior disorder can cause physical harm to the sleeping person, as well as to others. Symptoms of REM behavior disorder are movements such as punching, jumping from the bed, and making noises such as shouting, and laughing.