It lives 50 feet beneath the city. It's 36 feet long. It weighs 2,000 pounds...And it's about to break out!

Alligator (1980) - When a 10-inch baby gator from a Florida gift shop is flushed down the toilet, the ravenous reptile eats the dead corpses of test animals used in hormonal experiments and grows to prehistoric proportions. The massive monster emerges from the secrecy of the sewers to bring the end of civilization as we know it.
Alligator II: The Mutation (1991) - Deep in the sewers beneath the city of Regent Park, a baby alligator feeds on the experimental animals discarded by Future Chemicals Corporation. Nourished by the toxic growth hormones and other mutating chemicals, the gator grows immense in size ... and voracious in appetite. Now, it must kill to survive!