Baby's First Profanity

What do you do about a three-year-old who has gotten into the habit of saying, "I Don't Caaaayeeer!" in the worst little sing-song voice. I'm pretty sure he doesn't even know what it means, but the first time he said it, I told him that it wasn't nice to say and that was the kiss of death. I think he heard it once from M. when he was reprimanding him for something and Little Guy talked back and M. said, "I don't care if blah, blah, blah, you'll do it anyway..." something to that effect. So now he goes around the house and says it for no reason. He doesn't really use it correctly in response to anything so I guess that's good. I've taken to ignoring it because responding was kicking it into a new stratosphere of constant usage. Ignoring it has helped significantly. Maybe he'll get bored of it soon and move onto something else.