Penny wants to throw a surprise party for Leonard, but Sheldon’s indulgence at an electronics store throws her off-track.

Sheldon becomes agitated when his regular barber is out sick. Astronaut training causes Howard to reconsider wanting to go into space. Penny beats Leonard in chess, the first time she…

Penny tags along on Sheldon’s first ever date; Wolowitz finds a new use for a robotic arm.

Brilliant physicist roommates Leonard and Sheldon meet their new neighbor Penny, who begins showing them that as much as they know about science, they know little about actual living.

Howard and Bernadette welcome their new baby and Sheldon and Amy celebrate Amy’s birthday.