Penny inquires as to why Sheldon did not buy Leonard a gift for his birthday.

After Penny helps Sheldon with his show, Amy tells him to demonstrate appreciation for her help. Sheldon does so and complains about all of the social norms as he learns about more of them.

Sheldon's World of Warcraft account get hacked.

Howard buys the guys a “Fantastic 4” comic book to celebrate his upcoming marriage.

Penny buys Leonard & Sheldon a Star Trek Transporter.