Q-ster has made a kind of Nerf/Lego shop in his room, with his designs available for purchase, so Buster decided to open up a Snuggling Friends Shop. He was able to prevail upon his brother to write his store sign on a post-it to stick to his door.
Then he wrote this one himself, to put on the door when he's not available to open the shop.
"Dot (don't) come in. Nobody home!"