There were a variety of authors, much as is S.O.P. for television shows. I believe one Eric Knight was one of the first, and several canine-fiction writers, a genre that has well barked out of existence, pretty much.
Lassie Come-Home was written by Eric Knight.
Greensleeves. The song was used as the (Lassie) theme , by the way.
Lassie - 1954 Lassie and the Calf - 8.34 was released on: USA: 13 May 1962
Lassie - 1954 Lassie's Vanity - 3.19 was released on: USA: 13 January 1957
Lassie - 1954 Lassie's Day - 3.23 was released on: USA: 10 February 1957
Lassie - 1954 Lassie's Interlude - 17.1 was released on: USA: 20 September 1970
Pal has: Played Lassie in "Lassie Come Home" in 1943. Played Bill aka Duke in "Courage of Lassie" in 1946. Played Larry in "My Brother Talks to Horses" in 1947. Played Lassie in "Hills of Home" in 1948. Played Lassie in "Challenge to Lassie" in 1949. Played Lassie in "The Sun Comes Up" in 1949. Played Shep in "The Painted Hills" in 1951. Played Lassie in "Lassie" in 1954. Played Lassie in "50 Greatest TV Animals" in 2003.
Lassie was a Collie.
The first dog to play Lassie died in 1958 at the age of 18. The current Lassie, nicknamed Mason, appeared in the 2005 film with Peter O'Toole and is still alive. There were several dogs to play Lassie, it just was not one dog. The first dog who played Lassie was named "Pal" in 1943. Pal appeared in movies from 1943 to 1951, and in the pilots for the first TV series in 1954. Pal was bred to continue the look of Lassie. Eight generations of Pal and his descendants portrayed the beloved collie in two television series and ten movies, through the late 1990s.
Lassie - 1954 Lassie and the Bird Watch - 10.1 was released on: USA: 29 September 1963
Lassie - 1954 Lassie's Day 3-23 was released on: USA: 10 February 1957
Lassie - 1954 Lassie and the Greyhound 7-33 was released on: USA: 30 April 1961