You return him at noon on the day AFTER you rent him. Mine went all around Epcot, then went to PI with me for the night and got returned the next day.
When he giggles, you're supposed to squeeze his hand and he'll tell you a story. It's hard to hear him unless you sit him up on your shoulder. If there are others in the group who want to hear his story, squeeze his hand again and he'll repeat it. If you squeeze his hand when he hasn't giggled, he'll tell a terrible joke (all his jokes were pretty bad).