S12, E18: When competitors Pemberton and Campbell (guest stars SEAN ASTIN and KAL PENN) charm America on a publicity tour, Sheldon and Amy try to bring Nobel laureates KIP THORNE, GEORGE SMOOT and FRANCES ARNOLD to their side (this episode sets the record for most Nobel laureates appearing in a comedy). Meanwhile, Halley’s fear of the dark leads to both opportunity and conflict for Howard, Bernadette and Stuart.