I just noticed this on Katharine's door.
Around two weeks ago, Katharine, myself and the boys were playing a board-game called 'Descent', and Katharine and Lukas flipped out on Lennon when he got greedy and tried to get some extra treasure.
It's just a game, so after a quick reality check we paused and sent the kids to their rooms to cool off.
Katharine is such a sweet kid, and must have written the note at that time.
I'm such a clueless Dad, it ended up taking me around two weeks to even notice it :P