Long before The Big Bang Theory earned the ire of critics by betraying Penny’s life plans, the show did hint at this huge series finale twist with a throwaway joke from one season 8 episode. The Big Bang Theory’s finale mostly focused on Sheldon, even though Jim Parsons’ character was never originally intended to be the show’s primary protagonist. Sheldon’s Nobel Prize ceremony was central to the finale’s action, but everyone else got a subplot of their own. For most of The Big Bang Theory’s cast of characters, this meant a light-hearted storyline about dealing with Sheldon’s ego.
However, Penny’s finale fate was a little more divisive among the show’s viewers. The Big Bang Theory finale revealed Penny was pregnant despite the character spending years saying that she didn’t want to have children. This was no incidental character detail, with Penny’s disinterest in parenting anchoring numerous plots throughout the show’s final seasons. She and Leonard fought after he divulged this to her father, Leonard was crestfallen when she first addressed the issue, and both Amy and Bernadette insulted her personally after she shared her life plans. Thus, the finale’s twist came as a major surprise.
Although this plot twist might have seemed to come out of nowhere, The Big Bang Theory foreshadowed Penny’s pregnancy when Sheldon told her he thought of her as a mother sometimes. In season 8, episode 16, "The Intimacy Acceleration,” Penny and Sheldon tried an intimacy test to see if the pair would become closer friends afterward. They did, and the experiment proved that, although Penny’s Big Bang Theory character arc was disappointing compared to Sheldon’s, the pair’s friendship was the show’s strongest and most complex relationship. In the process, Sheldon shared that he occasionally thought of Penny as a mother.
It makes sense that Sheldon would have seen Penny as a maternal figure even if he wasn’t able to predict the future.
Penny dismissed the comment as creepy but failed to realize that it was also prescient. Sheldon treated Penny like a surrogate mother throughout the series as far back as season 1, episode 11, “The Pancake Batter Anomaly.” In that famous outing, Penny tended to a sick Sheldon and treated him with surprising warmth and compassion. In season 11, episode 5, “The Collaboration Contamination,” Penny used a parenting book to reshape Sheldon’s behavior. Thus, it makes sense that Sheldon would have seen Penny as a maternal figure even if he wasn’t able to predict the future.