Castellaneta became adept at impressions at a young age and his mother enrolled him in an acting class when he was 16 years old. He would listen to his father's comedy records and do impressions of the artists. He was a "devotee" of the works of many performers, including Alan Arkin and Barbara Harris and directors Mike Nichols and Elaine May. He attended Oak Park and River Forest High School and upon graduation, started attending Northern Illinois University (NIU) in the fall of 1975.
Castellaneta became adept at impressions at a young age and his mother enrolled him in an acting class when he was 16 years old He would listen to his father's comedy records and do impressions of the artists He was a "devotee" of the works of many performers including Alan Arkin and Barbara Harris and directors Mike Nichols and Elaine May He attended Oak Park and River Forest High School and upon graduation started attending Northern Illinois University (NIU) in the fall of 1975