Old Yeller-Belly

Santa's Little Helper fails to save Homer from Bart's treehouse fire. As a result, Homer disowns him, but when Santa's Little Helper becomes the newest mascot for Duff Beer (replacing Duffman), The Simpsons want him back--but may be too late when Santa's Little Helper's previous owner from the very first episode ("Simpsons Roasting over an Open Fire") wants his dog back too.