Evolution

Evolution (aka Evolution of the World) was an ambitious project conceived by legendary animator Ray Harryhausen.

Plot
The premise would follow the story of life on Earth, according to evolution.

Why It Was Cancelled
Because of his love of dinosaurs, Harryhausen animated them first. However, he saw Walt Disney's Fantasia and the way dinosaurs were portrayed in the "Rite of Spring" segment. Feeling that Disney had beat him to the punch, Harryhausen shelved the project.

Result
At least three minutes of footage survive today, but it also became a cover letter for Harryhausen when it later looked like work from a professional entertainer, and solidified his career as a stop-motion animator.