Thaddeus "Curly" Gammelthorpe is a fictional character in the Hey Arnold! TV Series. He is a fourth-grader who attends P.S. 118. He is in Arnold's class. Curly is most well known for his outlandish and bizarre behavior and freaking out to silly and trivial things (possible symptoms of psychosis, bipolar disorder, or borderline personality disorder). He is known as the "fourth-grader most likely to snap". He is considered one of the geeks ("Rhonda's Glasses").