The D & D Vortex: When the gang find out that Wil Wheaton is hosting a celebrity game of Dungeons & Dragons, and has invited William Shatner, deception and betrayal take hold. (S12 Ep16/24) [AD,S]
The Bow Tie Asymmetry: Everyone focuses on making sure all the arrangements for Amy and Sheldon's big day go according to plan, except the bride and groom. Mark Hamill guests. (S11 Ep24/24) [AD,S]
The Gates Excitation: The guys do everything in their power to meet guest star Bill Gates when his firm has dealings with the pharmaceutical company that Penny works for. (S11 Ep18/24) [AD,S]
The Celebration Experimentation: The gang make Sheldon celebrate his birthday and invite special guests - including Stephen Hawking, Adam West and Wil Wheaton - to his party. (S9 Ep17/24) [AD,S]
The Mystery Date Observation: While Amy is out on a date with a mystery man (guest star Stephen Merchant), Sheldon enlists Howard and Raj to help him find a new girlfriend. (S9 Ep8/24) [AD,S]
The Convention Conundrum: After the guys miss out on Comic-Con tickets, Sheldon decides to hold his own comic book convention. James Earl Jones and Carrie Fisher guest star. (S7 Ep14/24) [AD,S]
The Proton Displacement: Sheldon is jealous when Professor Proton (guest star Bob Newhart) asks Leonard to read his latest publication, so he befriends Bill Nye the Science Guy. (S7 Ep7/24) [AD,S]
The Holographic Excitation: The gang celebrates Halloween with a fancy dress party at the comic book shop, but Sheldon and Amy can't agree about costumes. Buzz Aldrin guests. (S6 Ep5/24) [AD,S]
The Hawking Excitation: When guest star Stephen Hawking comes to lecture at the university, Howard is given the task of maintaining his wheelchair, making Sheldon envious. (S5 Ep21/24) [AD,S]
The Hot Troll Deviation: An embarrassing secret of Howard's comes to light as he tries to win back his ex-girlfriend Bernadette. Katee Sackhoff and George Takei guest star. (S4 Ep4/24) [AD,S]
The Excelsior Acquisition: Sheldon is summoned to court for driving through a red light. He misses the chance to meet guest Stan Lee and riles the judge. Will he go to prison? (S3 Ep16/23) [AD,S]
The Gates Excitation: The guys do everything in their power to meet technology magnate Bill Gates when his firm has dealings with the pharmaceutical company Penny works for. (S11 Ep18/24) [AD,S]
The Celebration Experimentation: The gang persuade Sheldon to celebrate his birthday and invite special guests to his party, including Adam West, star of 1960s TV show Batman. (S9 Ep17/24) [AD,S]
The Platonic Permutation: At Thanksgiving, Sheldon and Amy hang out as friends at the aquarium. Howard volunteers at a soup kitchen, where he encounters entrepreneur Elon Musk. (S9 Ep9/24) [AD,S]
The Convention Conundrum: After the guys miss out on Comic-Con tickets, Sheldon decides to hold his own comic book convention. James Earl Jones and Carrie Fisher guest star. (S7 Ep14/24) [AD,S]
The Proton Displacement: Sheldon is jealous when Professor Proton asks Leonard to read his latest publication, so he befriends rival TV personality Bill Nye the Science Guy. (S7 Ep7/24) [AD,S]
The Proton Resurgence: Leonard and Sheldon hire Professor Proton (guest star Bob Newhart), the host of a TV science show they watched as children, to entertain them at home. (S6 Ep22/24) [AD,S]
The Holographic Excitation: The gang have a Halloween fancy dress party. Howard annoys everyone by constantly talking about his trip to space. Astronaut Buzz Aldrin guest stars. (S6 Ep5/24) [AD,S]
The Hawking Excitation: When Professor Stephen Hawking comes to lecture at the university, Howard is given the task of maintaining his wheelchair, making Sheldon envious. (S5 Ep21/24) [AD,S]
The Transporter Malfunction: Penny buys Leonard and Sheldon some Star Trek memorabilia but Sheldon dreams one of the action figures has a life of its own. Leonard Nimoy guests. (S5 Ep20/24) [AD,S]
The Hot Troll Deviation: An embarrassing secret of Howard's comes to light as he tries to win back his ex-girlfriend Bernadette. Star Trek actor George Takei guest stars. (S4 Ep4/24) [AD,S]
The Cruciferous Vegetable Amplification: Sheldon realises he won't live long enough to download his consciousness into a robot body. The gang bump into inventor Steve Wozniak. (S4 Ep2/24) [AD,S]
The Excelsior Acquisition: Sci-fi stars, tech wizards and eggheads feature in a look back at the show's geekiest guests. Spider-Man creator Stan Lee visits the comic book shop. (S3 Ep16/23) [AD,S]