"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 Conference Valuation" -- Pictured: Rajesh Koothrappali (Kunal Nayyar), Sheldon Cooper (Jim Parsons), Amy Farrah Fowler (Mayim Bialik) and Howard Wolowitz (Simon Helberg). When Penny and Bernadette go to San Diego for a pharmaceutical sales convention, Wolowitz is in charge of the kids. Also, Sheldon finds a book on experimenting on kids, and the guys plus Amy make a day of it, on THE BIG BANG THEORY, Thursday, March 7 (8:00-8:31 PM, ET/PT) on the CBS Television Network. Photo: Michael Yarish/Warner Bros. Entertainment Inc. © 2019 WBEI. 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.