Carrie Ingalls was played by identical twins!
Labor laws for children are pretty rigorous. To get around these laws the production team hired a set of identical twins – Rachel and Sidney Bush, and rotated them as need be. This practice is exceedingly common in Hollywood.
Michael Landon was a heavy smoker.
Wasn’t everybody a heavy smoker back in the ‘70s? Michael Landon was a chain smoker who would puff right up until action – frequently putting his cigarette out on the palm of his glove.