Night the heat went out

During the Arctic expedition, the boys ran into some trouble with their science station's heating system. This resulted in the infamous "night the heat went out". In order to keep their core body temperatures from falling, they were forced to sleep together naked. The boys agreed never to speak about it again. Howard seems particularly embarrassed by the event, but Sheldon mentions it matter-of-factly and Raj says that to him it was a bonding moment.