co-worker: why did you tell our pointy-haired boss we need to do more testing on the prototype?
dilbert: i didn't do anything of the sort.
co-worker: carl says you did.
dilbert: who is a better authority on what i said - a guy who wasn't in the room or me?
co-worker: good question. on one hand, carl is an idiot and a known liar. on the other hand, it is common for guilty people to say they are innocent.
dilbert: what do innocent people say when you accuse them of stuff?
co-worker: who knows? just do't do it again.
dilbert under distress: i didn't do it once!!!