The Teenage Mutant Ninja Turtles are a fictional team of four teenage anthropomorphic turtles, named after four Renaissance artists, trained by a large rat (Splinter) in karate. From their home in the storm sewers of New York City, they battle petty criminals, evil overlords, mutated creatures, and alien invaders while attempting to remain hidden from society.
They came into popular media when my children were young. Now that I have grandchildren, they are making a come-back and my 6 year old grandson wanted a turtle themed birthday cake.
According to comic book lore, the pet turtles were flushed down the toilet into the New York City sewer system where they came in contact with radioactive material and grew to be about 5'5" tall. Yes, the scenario is realistic.