Kaplan was raised in a Jewish family[1] in Flatbush, Brooklyn where his father was a "storefront lawyer" and his mother taught high school biology at Erasmus Hall.

Prior to committing to a career in professional writing, Kaplan taught English in Thailand.

[5] Starting in 1986, Kaplan interned for Spy magazine,[6] where his duties included mopping the floors and writing blurb-length film reviews.

Upon Futurama's cancellation, Kaplan went to work for the short-lived comedy series Andy Richter Controls the Universe, writing just one episode.

In his first year with Futurama, which was also the show's first season, Kaplan served as story editor on every episode.

That there's nothing so horrible that we can't get used to it and accept it as part of life (...) Zombie College is an environment where there are undead monsters running around and trying to eat your brain but everybody is o.k.

[8]Kaplan co-created The Drinky Crow Show, based on the Maakies comics by Tony Millionaire, for Adult Swim.

Kaplan was interviewed in 2020 by lifelong friend Roger Kimmel Smith (whose father, Robert Kimmel Smith, wrote the book The War with Grandpa, which in 2020 was adapted into a motion picture starring Robert De Niro).