Dreams of a Rarebit Fiend: The Pet
Cartoon drawn by Windsor McCay (famous for "Little Nemo in Slumberland") about a pet that won't stop eating and growing. Considered to be the first example of a giant creature terrorizing a city in film.
1921, silent, black and white, 707 seconds.
Final thought: better than the other Rarebit Fiend film on Wikipedia's page for the comic