I had one once, quite a while back now, where the message was normal...it was what was underneath it that was funny. It went like this, "Hello, you've reached CCT and I'm a little, (insert toilet flushing), busy right now. So leave your name, number and a message after the beep and I'll get back to you as soon as possible, (sound of water emptying out of the toilet)." I timed it perfectly I thought it was funny.
ETA: I wanted to say that I didn't do this while I was going, I just took my machine into the bathroom and did the message there.