Thank goodness I have W blue-sky lives

One can, I am told, have fun with hacked versions of Super Mario Bros.

Others might not: (warning: copious, but well-justified, NSFW language)

And if you think that hack is evil, take a gander at this:

Yes, there is an explanation of just WTF is going on there. And yes, there is a faster speedrun out there, but the one above is much more entertaining.