Carl the Collector Episode 11 The Puffball Collection/The Bottle Cap Collection >The night after returning from a weekend visit to Harold's, Carl realizes he has left behind his bottle cap collection. Unable to sleep, Carl continually interrupts Sheldon's sleep through a walkie-talkie for help, with each idea from Sheldon proving unsatisfactory to Carl. Sheldon helps Carl figure out why he feels bad about the missing bottle cap collection, with Carl realizing that he is worried about the collection's safety. Carl and Maude call Harold, who reassures Carl that he will keep the collection safe and return it in the morning.