Alligator

A baby alligator is flushed down a Chicago toilet and survives by eating discarded laboratory rats injected with growth hormones. The small reptile grows gigantic, escapes the city sewers, and goes on a rampage.
A baby alligator is flushed down a toilet and survives by eating discarded lab animals that have been injected with growth hormones. The now gigantic animal escapes the city sewers and goes on a rampage, pursued by a cop and a big-game hunter.