"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 Plagiarism Schism" -- Pictured: Amy Farrah Fowler (Mayim Bialik), Sheldon Cooper (Jim Parsons) and President Siebert (Joshua Malina). Kripke (John Ross Bowie) has proof that Dr. Pemberton (Sean Astin) plagiarized his thesis in college, and Sheldon and Amy aren't sure if they should turn him in or not. Also, Wolowitz is happily surprised to learn that Bernadette wasn't the only waitress at the Cheesecake Factory who had a crush on him back in the day, on THE BIG BANG THEORY, Thursday, May 2 (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 Inspiration Deprivation" -- Pictured: Leonard Hofstadter (Johnny Galecki), Sheldon Cooper (Jim Parsons), Amy Farrah Fowler (Mayim Bialik), Howard Wolowitz (Simon Helberg) and Rajesh Koothrappali (Kunal Nayyar). The concept of what it would mean for women everywhere if Amy were to win a Nobel Prize causes Amy to have a meltdown. Also, Koothrappali and Wolowitz try to relive the good old days after Wolowitz buys a scooter that looks like the one he had years ago, on THE BIG BANG THEORY, Thursday, April 18 (8:00-8:31 PM, ET/PT) on the CBS Television Network. Oscar-winning actress Regina King returns as Janine. Photo: Michael Yarish/Warner Bros. Entertainment Inc. © 2019 WBEI. All rights reserved.

"The Laureate Accumulation" -- Pictured: President Siebert (Joshua Malina), Professor Frances H. Arnold (Herself), Amy Farrah Fowler (Mayim Bialik), Leonard Hofstadter (Johnny Galecki), Sheldon Cooper (Jim Parsons), Dr. Pemberton (Sean Astin), Dr. Campbell (Kal Penn) and Professor Kip Thorne (Himself). When competitors Pemberton (Sean Astin) and Campbell (Kal Penn) charm America on a publicity tour, Sheldon and Amy try to bring Nobel laureates Kip Thorne, George Smoot and Frances Arnold to their side. Also, Halley's fear of the dark leads to opportunity and conflict for Howard, Bernadette and Stuart, on THE BIG BANG THEORY, Thursday, April 4 (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.

Credit: CBS/WB

"The Donation Oscillation" -- Pictured: Marissa (Lindsey Kraft), Zack (Brian Thomas Smith), Penny (Kaley Cuoco) and Leonard Hofstadter (Johnny Galecki). Penny tries to seduce an abstaining Leonard to ruin his "donation" for her ex-boyfriend, Zack (Brian Thomas Smith), and his wife, Marissa (Lindsey Kraft). Also, Wolowitz, Bernadette, Anu (Rati Gupta) and Koothrappali turn Koothrappali's canceled bachelor party into a couple's trip aboard the "vomit comet," on THE BIG BANG THEORY, Thursday, Feb. 7 (8:00-8:31 PM, ET/PT) on the CBS Television Network. Keith Carradine returns as Penny's father, Wyatt. Photo: Michael Yarish/Warner Bros. Entertainment Inc. © 2019 WBEI. 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 Confirmation Polarization" -- Pictured: Dr. Campbell (Kal Penn), Sheldon Cooper (Jim Parsons) and Pemberton (Sean Astin). When Sheldon and Amy's super asymmetry theory is proven by two physicists, Dr. Pemberton (Sean Astin) and Dr. Campbell (Kal Penn) from Chicago, they're thrilled, until they try to kick Amy off the Nobel nomination. Also, Bernadette has a big success at work and Penny's going to be a part of it -- whether she wants to or not -- on THE BIG BANG THEORY, Thursday, Jan. 17 (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 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 VCR Illumination" -- Pictured: Amy Farrah Fowler (Mayim Bialik) and Sheldon Cooper (Jim Parsons). Sheldon and Amy are still down about their theory being disproven, but a VHS tape from Sheldon's past inspires him not to give up. Also, Bernadette turns into a pageant mom when she tries to help Wolowitz ace his Magic Castle audition, on THE BIG BANG THEORY, Thursday, Dec. 6 (8:00-8:31 PM, ET/PT) on the CBS Television Network. Photo: Bill Inoshita/CBS ©2018 CBS Broadcasting, Inc. All Rights Reserved.

"The Consummation Deviation" - Pictured: Amy Farrah Fowler (Mayim Bialik), Mrs. Fowler (Kathy Bates) and Sheldon Cooper (Jim Parsons). Sheldon tries to bond with Amy's father, but when Wolowitz lures Mr. Fowler (Teller) away with magic tricks, Sheldon has no choice but to bond with Mrs. Fowler (Kathy Bates). Also, Koothrappali and Anu try to get physical for the first time, on THE BIG BANG THEORY, Thursday, Nov. 8 (8:00-8:31 PM, ET/PT) on the CBS Television Network. Photo: Sonja Flemming/CBS ©2018 CBS Broadcasting, Inc. All Rights Reserved.

"The Imitation Perturbation" - Pictured: Leonard Hofstadter (Johnny Galecki), Bernadette (Melissa Rauch) and Stuart (Kevin Susan). When Wolowitz dresses up as Sheldon for Halloween, Sheldon seeks retaliation at Leonard and Penny's Halloween party. Also, Leonard is shocked that Penny doesn't remember their first kiss, on THE BIG BANG THEORY, Thursday, Oct. 25 (8:00-8:31 PM, ET/PT) on the CBS Television Network. Photo: Michael Yarish/CBS ©2018 CBS Broadcasting, Inc. All Rights Reserved.

"The Planetarium Collision" -- Pictured: President Siebert (Joshua Malina) , Sheldon Cooper (Jim Parsons) and Amy Farrah Fowler (Mayim Bialik). When Amy doesn't have time to work on super-asymmetry, Sheldon goes to great lengths to ensure she's available to work with him even it if means accidentally sabotaging her career in the process. Also, Koothrappali doesn't want Wolowitz to join him in hosting a show at the planetarium, on THE BIG BANG THEORY, Thursday, Oct. 18 (8:00-8:31 PM, ET/PT) on the CBS Television Network. Emmy Award winner Bob Newhart returns as Arthur Jeffries. Photo: Michael Yarish/Warner Bros. Entertainment Inc. © 2018 WBEI. All rights reserved.