: Sheldon and Amy formalize their unique bond with a "Relationship Agreement," while Howard and Bernadette prepare for their wedding, culminating in Howard's mission to the International Space Station.
: While his friends find partners, Raj continues to struggle with his selective mutism, even attempting to find companionship through a mobile phone's virtual assistant. Cast & Guest Appearances The Big Bang Theory Season 5 Complete Pack
: Laurie Metcalf returns as Mary Cooper, and Christine Baranski reprises her role as Leonard’s mother, Beverly. "Complete Pack" Features : Sheldon and Amy formalize their unique bond
: Amy Farrah Fowler (Mayim Bialik) and Bernadette Rostenkowski (Melissa Rauch) are promoted to main characters, providing a female social circle for Penny that mirrors the guys' group. "Complete Pack" Features : Amy Farrah Fowler (Mayim
: The milestone episode, "The Recombination Hypothesis," sees Leonard and Penny attempt a "beta test" of their relationship after their initial breakup, marking a central narrative shift for the series.
: Leonard Nimoy provides the voice for a Sheldon-sized Spock action figure, and Brent Spiner appears alongside series regular Wil Wheaton .
: Stephen Hawking makes his legendary first on-camera appearance, while astronaut Mike Massimino joins as a recurring guest during Howard’s space arc.