Toto is a fictional dog in L. Frank Baum's Oz series of children's books, and works derived from them.
Lassie is a fictional female collie dog character created by Eric Knight in a short story expanded to novel length called Lassie Come-Home.
Laika was a Soviet space dog who became one of the first animals in space, and the first animal to orbit the Earth.
Pluto, also called Pluto the Pup, is a cartoon character created in 1930 by Walt Disney Productions.
Dogmatix or Idéfix (French) is a fictional character in the Asterix comics.