Child 2: "MAMA! There's something really important I want to say. I have FOUR words I want to tell you. ONE of them is a grownup word, TWO of them are regular words, and ONE of them is a mean word. Except..... you're not going to like it...."
Me: "I'm not going to like what, the grownup word?"
Child 2: "No, you won't like that word. It's a really bad word."
Me: "Well, if you know it's a bad word, and you're not supposed to say it, then you shouldn't say it."
Child 2: "Okay. But, I want to say it, except it's really bad. It's... the one that starts with 'f' "
Me: "The one that starts with 'f'? That's the worst word of them all! You aren't supposed to say that word and you know you're not supposed to say that word!"
Child 2: "Okay, I won't say that word. But I really wanted to tell you something."
Me: "Okay, tell me the other three words."
Child 2: "Shut..... theeeeeeeee ........................................................ up."
Me: fall over laughing, despite myself