People love dogs, and none is as beloved as Lassie. She’s been a pop-culture star since 1938, when the courageous collie first appeared in a short story.She made her 1943 film debut in MGM’s “Lassie Come Home,” co-starring Roddy McDowall and Elizabeth Taylor. That hit spawned films, a radio show and, later, a hit TV series. Lassie has been onscreen for more than 60 years. Part of the key to her success is her breed: She’s a work dog, so she is smart and loyal, and beautiful — appealing to boys and girls. Lassie is one of three animals to have a star on the Hollywood Walk of Fame (silent-era stars Rin Tin Tin and Strongheart are the others).