Elizabeth Taylor replaced Maria Flynn for the role of Priscilla. Some sources say Flynn was afraid of the dog on the set. Others say that she grew taller than Roddy McDowall or that the strong Technicolor lighting caused her eyes to water. In any case, production was halted. The producer was walking the 600 block of North Foothill Road in Beverly Hills doing his nightly patrol as an air raid warden when he met Francis Taylor, who patrolled the 700 block. Knowing he and Sara wanted to get their daughter into the movies, he asked him to bring Elizabeth to the studio. There she was introduced to Lassie and the production resumed.
After a nationwide hunt for a suitable dog for this movie failed, MGM called in dog trainer Rudd Weatherwax, who had many purebred collies, but Pal, his one-year old male collie (who had no papers), easily won the role. Pal retired at age 5, after which all subsequent Lassie films used direct descendants of Pal.
Pal who portrayed Lassie earned a salary of $250 per week while the young Elizabeth Taylor was paid a mere $100 per week.
The number of purebred collies registered in the United States in the late 1940s increased from 3,000 to 18,400, probably because of the Lassie series of films.
Though Lassie is supposed to be a female dog, this and all subsequent Lassie films have used male dogs to play her, supposedly because males are easier to train.