Do Not Fort Sake Me / Cookie D'uh

S1 E3: Coop and Dennis build a tree fort to get some Kat and little sister-free time, but Kat tricks them into leaving the fort and she takes over, using all the Kat defenses they so cleverly installed to keep the boys from reclaiming their fort. Millie sells a record number of Greenie Girl Cookies but the boxes keep disappearing and all fingers point to Coop.