I have a little saying in my room that comes in very handy when a little person is awfully concerned about what everyone else is doing. They want to tell me what so and so is up to, and sometimes they even want to tell so and so about it too. In one of these moments, I like to say, "It's called self-control, not (insert name of child they are tattling on) -control." It works pretty well, and it's even better when they can finish my sentence. "It's called self-control, not..." I pause and the child takes it from there.
While we're on the subject of self-control, have you heard of self-control bubbles? Check them out here and another post about self-control here too. It's a great time of year to remind our little ones about such things. :)