Philip Dey "Phil" Eastman was an American screenwriter, children's author, and illustrator, known primarily under his pen name P. D. Eastman. Born in Amherst, Massachusetts, Eastman graduated from Amherst College in 1933 and went on to study at the National Academy of Design in New York City. His career in animation and storytelling began in 1936 at the Walt Disney Studios where he worked in production design, story, and as an assistant animator. Here, he met his future wife, Mary Louise Whitham, who was working in the color model department.

In 1941, Eastman moved to Leon Schlesinger Productions (later Warner Brothers Cartoons), where his work continued to evolve. His service in the Army during World War II saw him assigned to the Signal Corps Film unit, where he worked under Ted Geisel (Dr. Seuss), the head of the unit. Eastman contributed significantly to the "Private Snafu" series and was a driving force in the animated storytelling of that era.

Post-war, Eastman joined United Productions of America (UPA), contributing as a writer and storyboard artist. Notable works during this period include writing for the animation Mr. Magoo, and co-writing the screenplay for "Gerald McBoing-Boing," which won an Oscar for Best Animated Short Subject in 1951. His freelance work began in 1952, with significant contributions to comic books for Whitman Publishing and later, TV commercials.

The latter part of Eastman's career was marked by his affiliation with Ted Geisel's BEGINNER BOOKS series at Random House, culminating in the publication of his first children's book, "Sam and the Firefly," in 1958. His distinct style and contributions to children's literature under the Dr. Seuss brand have left an indelible mark on the genre.