I chalk these questions up to pure, unadulterated ignorance. I'll tolerate a person asking me each of these questions once but after that I start sending them blog links (like the one where Greta Christina blew threw a list of questions never to ask an atheist) and links to youtube videos like this. It's not my job to teach them what atheism is, that's what the internet is for.
Teenaged X-Files obsession + Bermuda Triangle episode + Self-led school research project = Atheist.