The Promise is an episode.
When Little Bill runs out of his own belongings to bring to Show and Tell, he asks his sister April if he can borrow her basketball trophy to show. Bobby points out that the trophy is April's most prized possession, but April gives her permission and makes Little Bill promise to take care of the trophy. Unfortunately, despite Little Bill telling his friends that they couldn't touch the trophy after he showed it to them, somehow it gets misplaced during recess and the little basketball on the player's hand gets broken off. Little Bill is afraid April will be angry with him for breaking his promise, but Bobby suggests they try to fix the trophy. Little Bill sacrifices his most prized possession, a tiger's eye marble, to replace the missing basketball on the trophy, and his sister forgives him.