"The Maternal Conclusion" -- Pictured: Leonard Hofstadter (Johnny Galecki), Beverly (Christine Baranski) and Sheldon Cooper (Jim Parsons). Leonard is pleasantly surprised when Beverly (Christine Baranski) comes to visit and she's genuinely kind to him, until he finds out the real reason she's there. Also, Denise and Stuart overstay their welcome at the Wolowitz house, on THE BIG BANG THEORY, Thursday, May 9 (8:00-8:31 PM, ET/PT) on the CBS Television Network. Photo: Michael Yarish/CBS ©2019 CBS Broadcasting, Inc. All Rights Reserved

"The Decision Reverberation" -- Pictured: Anu (RatI Gupta) and Rajesh Koothrappali (Kunal Nayyar). Koothrappali is worried people won't take him seriously in his own field after publishing a paper that suggests he may have discovered alien life. Also, Leonard wants to be the principal investigator on a plasma physics study, on THE BIG BANG THEORY, Thursday, April 25 (8:00-8:31 PM, ET/PT) on the CBS Television Network. Photo: Michael Yarish/CBS ©2019 CBS Broadcasting, Inc. All Rights Reserved .

"The Meteorite Manifestation" -- Pictured: Sheldon Cooper (Jim Parsons), Rajesh Koothrappali (Kunal Nayyar), Howard Wolowitz (Simon Helberg) and Leonard Hofstadter (Johnny Galecki). Sheldon is thrilled to help Bernadette and Wolowitz navigate bureaucratic paperwork, until he discovers they are breaking the law. Also, Leonard is disappointed when his friends exclude him from a scientific project, on THE BIG BANG THEORY, Thursday, Jan. 31 (8:00-8:31 PM, ET/PT) on the CBS Television Network. Andy Daly guest stars as Nathan. Photo: Sonja Flemming/CBS ©2019 CBS Broadcasting, Inc. All Rights Reserved

"The Propagation Proposition" -- Pictured: Anu (Rait Gupta) and Rajesh Koothrappali (Kunal Nayyar). Penny's ex-boyfriend, Zack (Brian Thomas Smith), and his wife want a baby, but when Zack is infertile, they ask Leonard for help. Also, Koothrappali attempts to mend things with his ex-fiancée, Anu (Rait Gupta), on THE BIG BANG THEORY, Thursday, Jan. 10 (8:00-8:31 PM, ET/PT) on the CBS Television Network. Photo: Michael Yarish/Warner Bros. Entertainment Inc. © 2018 WBEI. All rights reserved.

"The Paintball Scattering" - Pictured: Amy Farrah Fowler (Mayim Bialik), Sheldon Cooper (Jim Parsons), Leonard Hofstadter (Johnny Galecki) and Penny (Kaley Cuoco). Penny and Leonard organize a paintball game that results in mayhem when Sheldon is jealous of Amy. Also, Koothrappali catches Anu with her ex-boyfriend and Stuart doesn't want to move in with Denise, on THE BIG BANG THEORY, Thursday, Jan. 3 (8:00-8:31 PM, ET/PT) on the CBS Television Network. Photo: Michael Yarish/Warner Bros. Entertainment Inc. © 2018 WBEI. All rights reserved.

"The Tam Turbulence" -- Pictured: Bernadette (Melissa Rauch) and Penny (Kaley Cuoco). When Sheldon won't tell anyone why he's never mentioned Tam (Robert Wu), his childhood best friend, Leonard takes matters into his own hands. Also, Bernadette and Penny take out Raj's fiancée, Anu (Rati Gupta), for dinner to get the skinny on her, on THE BIG BANG THEORY, Thursday, Oct. 11 (8:00-8:31 PM, ET/PT) on the CBS Television Network. Jerry O'Connell returns as Sheldon's brother, George. Photo: Michael Yarish/CBS ©2018 CBS Broadcasting, Inc. All Rights Reserved.