Sewer Alligators

Wealthy families would return from vacation from Florida and ignore the laws in New York City, bringing alligators with them, as pet presents to their children. The time frame of this tradition is rather gray, but it has been suggested it originated in the late 1930s. When the alligators grew too large for comfort, the family would proceed to dump them down storm drains. The alligators survive and reside within the sewer and reproduce, surviving by feeding on rats and rubbish, growing to huge sizes. -//edited from wikipedia