This isn't the best example, but it's the only one I can think of off the top of my head:
Someone: "I seriously think 2012 is going to happen." (y'know, world ending, blah blah blah)
Me: "Yeah, it will come right after 2011 and just before 2013."
Not the funniest, but he got angry with me
If he was my friend, he would've understood that it's just what I do and I don't mean any offence by it.