Lol. When they start labelling EVERYTHING (if they don't already) start scribbling out their name and writing yours then act like you have no idea what they are talking about. Make sure you can see remnants of their name under the scribble just to add to the conviction in their argument! There's something funny about an adult pointing at a scribbled out name on a banana angrily saying "LOOK my name you CAN see it!!" :p