I found that when the kids are having a bad repetitive behavior like that, giving them an alloted time to get it out of their systems really works. For instance, my four year old isn't allowed to say words like "poop" at the dinner table, but she can use "potty talk" all she wants in the bathroom. When she was younger she would snort like a pig when people were trying to talk to her, so before we had guests over I would give her ten minutes to snort like a pig as much as she could, with the understanding that it was her last chance to do so for the day. She thought it was really funny and it stopped the misbehavior.