You've seen the Little Rascals / Our Gang children's comedies of the 40's - Spanky, Alfalfa and all. . . but I'll bet you remember the dog best, if only for the funny circle around one of his eyes.
His name was Petey, and he (and his descendants) were pit bulls. Learn a lot about him here.
(I don't recommend going to the pit bull link called "Sad Reality," unless you want to spend some time really hating some people.)
Pete the Pup even has his own page at the Internet Movie Database, where you learn that he was in "The Slippery Pearls," "Cat, Dog & Co.," and "Buster Minds the Baby," among a bunch of other little movie gems.