The Sun Comes Up is a 1949 Metro-Goldwyn-Mayer Technicolor picture with Lassie. Jeanette MacDonald had been off the screen for five years until her return in Three Daring Daughters (1948), but The Sun Comes Up was to be her last. In it, she had to share the screen not with an up-and-coming younger actress but with a very popular animal star. Although her retreat from a film career can be blamed largely on an increasingly debilitating heart ailment, MacDonald continued to make concert and TV appearances after this. Her last radio performance was a broadcast version of this same story on The Screen Guild Theater in March 1950.

Lassie is a fictional female Rough Collie dog and is featured in a 1938 short story by Eric Knight that was later expanded to a 1940 full-length novel, Lassie Come-Home. Knight's portrayal of Lassie bears some features in common with another fictional female collie of the same name, featured in the British writer Elizabeth Gaskell's 1859 short story "The Half Brothers". In "The Half Brothers", Lassie is loved only by her young master and guides the adults back to where two boys are lost in a snowstorm.