Lassie, a female collie, first appeared in a novel entitiled Lassie, Come Home by Eric Knight. Adapted to the big screen, she debuted in 1943 and was portrayed by a dog named "Pal". The Emmy winning series Lassie debuted in 1954 and ran for 19 years. Descendants of "Pal" played the lead over the years and continue to tour today. Lassie had many owners over the years: initially owned by Jeff (Tommy Retting) and his widowed mom (Jan Clayton) they lived on a farm; next the owner was Timmy (Jon Provost) and adoptive parents (Cloris Leachman and Jon Sheppod and later June Lockhart and Hugh Reilly); in the 60's the show was filmed in color and the storyline changed to have Lassie work with forest service rangers and her new owner was Ranger Corey Stuart (Robert Bray). The theme of each episode was Lassie saves the day. June Lockhart was quoted as saying Lassie is "a fairy tale about people on a farm in which the dog solves all the problems in 22 minutes, in time for the last commercial."
In researching the information about the series I found it interesting that some parent watch-dog groups protested the cliffhanger plots as too intense for young viewers. My mother made me quit watching it because I always cried when Lassie seemed to be hurt. Her reassurance that Lassie was always okay just wasn't enough.