A 67-year-old man with progressive ataxia and dysarthria was diagnosed with Creutzfeldt-Jakob disease based on genetic testing. This video illustrates notable physical examination findings of negative myoclonus and a severe, low-frequency, high-amplitude wing-beating tremor elicited by sustained left arm abduction with flexed elbows and palms facing downward. The tremor is classically attributed to Wilson disease. Go to https://ja.ma/3djszUx for complete case details and discussion.