Casella was born in Washington, District of Columbia, the son of David Deitch (a newspaper columnist) and Doris Casella (a social worker). His father is Jewish and his mother is of Italian descent. He grew up in Cambridge, Massachusetts, where he attended the same school as Traci Bingham and Matt Damon.
Career
He is known for his roles on the television series The Sopranos, Boardwalk Empire, Doogie Howser, Doctor of Medicine and the voice of Daxter in the Jak and Daxter video game series. Casella played Vincent "Vinnie" Delpino in the television series Doogie Howser, Doctor of Medicine from 1989 to 1993 with Neil Patrick Harris. In 1992, Casella played Racetrack Higgins in Newsies, which was based upon true events in the 1899 newsboys strike against Joseph Pulitzer and William Randolph Hearst.
He appeared in WindRunner: A Spirited Journey, starring Margot Kidder and Russell Means as Jim Thorpe"s ghost.
From 2000 to 2001 he returned to Broadway as Marcellus Washburn in the revival of The Music Manitoba Casella portrayed Private
Dino Paparelli in Sergeant Bilko. He joined the cast of the Home Box Office series The Sopranos during its third season, as Benny Fazio.
Casella also starred in Editor Wood and Analyze This.
In 2007, Casella plays Dick Howser in the Entertainment and Sports Programming Network mini-series The Bronx is Burning. He also voiced Tip in The Little Mermaid II: Return to the Sea, Zini in the Consultants to Government and Industry film Dinosaur and the titular character in American Broadcasting Company"s Cro. In 2008, Casella played Mack Steiner in Leatherheads and Dennis, one of the main characters in Scaring the Fish.
He also played Leo Doctorate"Alessio in season one of the Home Box Office series Boardwalk Empire.