Alligator (1980)
Director: Lewis Teague
Writers: John Sayles (screenplay), John Sayles
Stars: Robert Forster, Robin Riker, Michael V. Gazzo.
Plot: A baby alligator is flushed down a Chicago toilet and survives by eating discarded lab rats, injected with growth hormones. The small animal grows gigantic, escapes the city sewers, and goes on a rampage.