The Little House on the Prairie TV show first aired on May 30, 1974 for what was a two hour pilot episode in the form of a TV movie for a potential full series. The show was picked up for a full season following the pilot episode, and the show officially began airing as a full television series on September 11, 1974.
The primary cast all appeared in the pilot episode, and the casting remained unchanged when it transitioned to a regular tv series.