When I was a kid there was as rumor going around that a woman saw a snake in the toilet at a Waldbaum's supermarket. The story became embellished with the claim that it bit her on the tushy.

There were also many rumors about alligators in the New York City sewer system. The legend was that baby alligators, which had been brought back from Florida as children's pets, were flushed down toilets when they became too big to keep, and ended up thriving in the sewers.

Alligators in the Sewer - An Urban Legend