The Big Bang Theory's finale had a fun callback to its first episode 12 years ago, via Penny's (Kaley Cuoco) wardrobe. CBS' long-running sitcom finally bowed out with an one-long special send-off that resolved a couple of the lingering plots of the series, including Amy (Mayim Bialik) and Sheldon's (Jim Parsons) bid for the Nobel Prize in Physics for their work on Super Asymmetry. The elevator was also finally fixed after more than a decade of the gang going up and down four flights of stairs. But another great surprise announcement made in the back half of the series finale was the reveal that Penny and Leonard (Johnny Galecki) are expecting a baby.
This came as a surprise for a lot of fans of the Hoftsadter couple, since much of their arc in final season was about their conflicting views on wanting a kid. Penny didn't want to have children, while Leonard was adamant about having one, hoping that he'd be able to provide a different childhood to his offspring than the one he had. The Big Bang Theory didn't tackle the issue in its final episodes, making fans feel that the couple simply agreed to disagree. This unexpected turn of events pays off Leonard's prediction that he and Penny will have smart and beautiful babies shortly after they met each other in the sitcom's premiere - something that Sheldon mentioned in his Nobel acceptance speech. But that wasn't the only homage the series finale had to the pilot.
Following the Pasadena gang's trip to Stockholm to join Amy and Sheldon accept their Nobel, The Big Bang Theory ended with all seven back home to Apartment 4A, eating Chinese food and chatting with each other, just like they always do. The camera then slowly pulled back with an acoustic version of the sitcom's theme song playing making for a touching final shot. However, the show included one more Easter egg in this parting sequence by having Cuoco wear the same aquamarine shirt she was wearing in the show's premiere. After Sheldon and Leonard come back home from the sperm donation bank, the two noticed that a new tenant moving into the apartment opposite theirs. There, a young Penny was sifting through her boxes as the boys introduced themselves. Leonard became infatuated then and there - although it took Penny a few more years to genuinely fall for her future husband
Penny has worn the shirt one more time in the course of the 12 years that The Big Bang Theory ran, during the 100th episode where she agrees to go out with Leonard, but that doesn't diminish the nostalgia factor seeing her sport it again at the very end of the show. Much more so seeing her interact with Leonard knowing their history together and the future that lies ahead for them. Throughout the course of the show, their mismatched marriage had been the butt of countless jokes - most of them done in poor taste. Aside from that, their story as a married couple had been sidestepped in the final couple of years, leading to the baby dilemma that ultimately didn't lead anywhere.
Not all fans of The Big Bang Theory are happy with how Penny and Leonard's story ended. Since Penny had spent so much of the season being adamant that she didn't want a baby, her sudden 180 on the topic upon finding out she was pregnant rang false for some. Still, as mundane as seeing Penny wear the same shirt she did the day she met Leonard was, it's a thoughtful reminder of how far they've come as individuals and as a couple in the show.