In the first of two back-to-back episodes, scientists Sheldon Cooper (Jim Parsons) and his wife Amy (Mayim Bialik) got the news that they are receiving the Nobel Prize in physics for their theory of super asymmetry, reports variety.com.
The final episode aired internationally on Thursday.
However, the two don't react very well to the news, especially Cooper. One recent development he doesn't take in his stride is the now-functional elevator, the disrepair of which had been a running gag on the show since its first season.
Although earlier Penny (Kaley Cuoco) told her husband Leonard (Johnny Galecki) that she never wanted kids, part 2 of the finale reveals that she is pregnant.
But when Cooper dismisses her announcement, Leonard angrily says "to hell with" his Nobel Prize. When his friends threaten to leave at his poor treatment of them, Sheldon takes time to self reflect.
At the Nobel ceremony in Sweden, Amy encourages little girls "who dream about sciencea to go for it. In a cameo appearance, Sarah Michelle Gellar sits next to Raj (Kunal Nayyar) in the audience, but assures him it's "not a date".
Cooper gives a heartfelt acceptance speech that, to fans who have been tuning in since the show's beginning, shows how much the character has grown out of his egotistical and selfish personality over the course of 12 seasons.
"I was under a misapprehension that my accomplishments were mine alone. Nothing could be further from the truth. I have been encouraged, sustained, inspired and tolerated, not only by my wife, but by the greatest group of friends anyone ever had," he said.
According to variety.com, Cooper then asks his friends, including Leonard, Penny, Raj, Howard (Simon Helberg) and Bernadette (Melissa Rauch) to stand.
"I apologize if I haven't been the friend that you deserve. But I want you to know, in my way, I love you all."
The second part ended with the gang hanging out in Leonard's living room and eating Chinese takeout. And fittingly, a version of the show's theme song by the Barenaked Ladies drew the episode, and the show, to a close.
"The Big Bang Theory" was launched in 2007. The show has received 52 Emmy Award nominations and 10 wins, seven Golden Globe nominations, and the spinoff prequel "Young Sheldon".
The show can be streamed on HOOQ in India. The finale episode will air in India on Zee Cafe on Saturday.