"Knock your heads together"- I remember this one from those long car trips that would devolve into "She touched me" "But she looked at me" kind of arguments.

When my parents raised their voice like that, you didn't want to wait for the countdown.

And yeah, I found it slipping out when I had kids of my own. That's when it really sunk in that I had become my mom despite years of rebellion, LOL.