The dog who played the character of "Lassie" on television was a (male!) rough collie. Lassie is a collie A rough Collie collie Lassie was a Collie (rough variety).
The dog in the movie 'the Shaggy Dog' comes from a Tibet monastery so the logical conclusion is that it's a Dokhi Apso, a very old Tibetan breed that is known in the west as Tibetan terrier. Although...
well, you have to make them have sex first. the way you do that is to put them alone in the same room, turn the lights off, put some "bow chicka wow wow" kind of music on, and just let the magic...