Okay, I've got a new one for bizarre customer conversation, though to be fair I had it with a four year old at work today.
I was busy feeding and watering the little fuzzies, and this kid toddles up to me (his mom is about six feet away, reading a package of rat food, so he's not unsupervised or anything. Since the mom is right there, I ask her if it's okay if I let him pet one of the rats, and she says it's fine. Then the following conversation occured:
Kid: He's nice!
Me: I know. Actually, it's a girl rat, though.
Kid: I want to get a rat with really sharp teeth.
Me: Why?
Kid: I also want to get a beaver!
Me: I'm pretty sure we don't sell beavers.
Kid: Well, where do beavers live?
Me: They live in creeks and rivers and build dams
Kid: Them I'm gonna go put my swimming suit on, go to the creek, and pick out the best one!
(The mother is cracking up at this point)
Me: Well, uh, that's the standard procedure for choosing a pet beaver.
Not exactly a "stupid customer story", but it definitely makes my list of interesting conversations.