Pipes (Mario Bros. series)
All video games typically demand from us a suspension of disbelief--especially ones involving a plumber that can travel through sewage pipes to magical, otherworldly lands. Following the logic of Mario games, folks might expect that a brief trek through liquid fecal matter could lead to hidden treasures and plenty of gold coins. All it would really lead to, though, is an introduction to E. coli, the Ebola virus, permanent pink eye, or a host of other poop-related diseases.
Then there's the bit about fitting into a pipe. Obviously there are pipes large enough to accommodate for a human's exploratory needs, but they're typically closed into circuits through which we cannot pass. And, even if we could, they would almost certainly lead to nothing but stinky tragedy.