You know that old saying, if you gave an infinite number of monkeys an infinite amount of time and typewriters they'd eventually produce Shakespeare? Well, we gave the World Wide Web about a decade and they've given us Teenage Mutant Ninja Noses. Thank you, Internet.
It's simple, really. Someone took a good long look at a picture in a magazine and said to themselves: I'm pretty sure there's a Teenage Mutant Ninja Turtle in that nose. And, you know what, he or she was kinda right.