Hurt Two Birds with a Rock

Me: "Come on, turn off the TV.  It's time to fix your hair."
Katie: "But, Mooooooom.  I want to finish 'Ponyo'.  It's almost over."
Me: "No, it's time to fix your hair now, not later."
Katie: "Why don't we do that thing, you know, that thing?  Where you hurt two birds with a rock?"
Me: "Kill two birds with one stone?"
Katie: "Yes!  Kill two birds with one stone.  You can fix my hair while I sit here and finish watching the movie."
Me: "There you go again.  You and your good ideas."