He was working in the script department at CBS in the 1950s and had written several plays that found a place in Los Angeles theatre, including La Peregrina, Victorey, The Root of the Iceplant, and The Hamster of Happiness.
The Hamster of Happiness became a screenplay produced at NBC as an Experiment in Television, with Susan Tyrrell and Mildred Dunnock, and later a motion picture at Lorimar under the title Second-Hand Hearts, directed by Hal Ashby.
[2] He is considered one of Hollywood's most accomplished script doctors;[citation needed] examples of this uncredited work include Otto Preminger's Bunny Lake Is Missing as well as The Loved One, The Cincinnati Kid, The Americanization of Emily,[2] This Property Is Condemned,[2] Who'll Stop the Rain, The Planet of the Apes and Heaven Can Wait.
[citation needed] Other original screenplays by Eastman include April 17, 1961, The Hundredth Monkey, Cowboy Christmas, and Kazhiamira and the Night Guys.
Other produced plays he wrote include The Un-American Cowboy, Busy Bee Good Food All Night Delicious, and Borders.