In actuality, the man is an accomplished performer on the stage, having won a Tony Award for his singing contributions. However, it would be his role as George Costanza, Jerkass extraordinaire and best friend to main character Jerry Seinfeld that would make Alexander a true household name. Being named "the greatest sitcom character of all time" by none other than Ricky Gervais, Alexander's accolades for the role included Emmy and Golden Globe nominations, as well as a win at the Screen Actors Guild Awards. One could say that, along with Michael Richards as Kramer, he became a Breakout Character on the show.
His son Gabriel Greenspan is also an accomplished actor.
He's also an expert poker player.
- The Burning (1981) as Dave
- The Mosquito Coast (1986) as a Clerk
- Pretty Woman (1990) as Philip Stuckey
- Jacob's Ladder (1990) as Geary
- Coneheads (1993) as Larry Farber
- Aladdin: The Return of Jafar (1994) as the voice of Abis Mal
- North (1994) as North's father
- Dunston Checks In (1996) as the dad and hotel manager
- The Hunchback of Notre Dame (1996) as the voice of Hugo
- Love Valour Compassion (1997) as Buzz Hauser
- Shallow Hal (2001) as Mauricio Wilson
- Everythings Relative 1987 as Julian Beeby
- Seinfeld (1990-1998) as George Costanza
- Aladdin: The Series (1994-1995) as the voice of Abis Mal
- Duckman (1994-1997) as the voice of Duckman
- Star Trek: Voyager, "Think Tank", (1999), as Kurros
- Dilbert (1999-2000) as the voice of Catbert
- Curb Your Enthusiasm (2001, 2009) as himself
- Listen Up (2004-2005) as Tony Kleinman
- Everybody Hates Chris (2006-2007) as Principal Edwards
- Young Sheldon (2018, 2020) as Gene Lundy
- Harley Quinn (2019) (2019-2020) as Sy Borgman
Tropes associated with Jason Alexander include:
- Name's the Same: He did not briefly marry Britney Spears.
- The Cast Show Off: He's a former Tony-winning Broadway actor with a great singing voice and occasionally shows it off.
- Two First Names: His Stage Name, Jason Alexander.