I am going to say this out right - the following post is fairly silly.
Anyway, just a few moments ago, I was messing with the stylesheets of a website I'm making. Just to see if it'd work, I changed the enclosing <html></html> tags to <lolhey></lolhey>. And it worked, in all of the browsers I've tried it with.
Then, I immediately made some CSS statements so <sarcasm></sarcasm> was the equivalent of <i></i>, and so that <yell> was the equivalent of <b>.
Of course, this would not work for complex tags like <table> or <img>, but it's fun making alternate tag names to confuse people reading your source.