Sheldon goes to Las Vegas to win money for science; Penny and Bernadette take Amy wedding dress shopping, but her terrible choice entangles them in a web of lies.
After dating for more than five years, Amy and Sheldon spend the night together for the first time; Leonard, Wolowitz, and Koothrappali must decide what to do with an extra movie ticket.
Amy realizes she has feelings for Penny's ex; Koothrappali and Wolowitz try to prove who would be a better superhero.
Sheldon tries to help Penny understand Leonard's work; Wolowitz gets jealous when Leonard starts hanging out with his new girlfriend.
Leonard is horrified when his mother (Christine Baranski) visits.