He has worked on Nickelodeon's SpongeBob SquarePants and on Cartoon Network's The Grim Adventures of Billy & Mandy and Evil Con Carne.

[4] Greenblatt collaborated with Maxwell Atoms on his new Billy & Mandy spin-off Halloween special called Underfist, in which he reprised his role as Fred Fredburger.

He announced on his blog that Nickelodeon has given the go-ahead for an 11-minute pilot for a new show created by him entitled Bad Seeds (later renamed Harvey Beaks).

[6][7] On October 29, 2019, the project was officially unveiled under the title of Jellystone!, described as a crossover of several Hanna-Barbera characters living in the titular town "where they can't help but make trouble for one another".

He helps mentor show creator, Joe Kozdra, in animation and creative writing alongside his voice-acting contributions.