Young Sheldon, The Big Bang Theory universe is only growing.
With 12 seasons to its name, The Big Bang Theory had both meaningful and steady storylines, along with brief and senseless storylines. Whether the arc was serious or insignificant, fans appreciated the show's growth over time and had their favorite storylines in each season.
Season 1: Penny & The Gang Getting Used To Each Other
Compared to other seasons, season 1 was TBBT's shortest season with 17 episodes. Season 1 was all about introducing the characters and what their connection was to each other. With the introduction of Sheldon and Leonard's new neighbor Penny, fans loved the ongoing storyline of apartments 4a and 4b getting used to each other.
Penny had to get used to how brilliant Leonard and co. were, while Leonard and Sheldon had to get used to having someone as beautiful as Penny around. While other things from season 1 of TBBT got worse, this storyline got better.
Season 2: Penny's Gaming Addiction (And Getting Closer To Sheldon)
In season 2, Penny became much closer with Leonard, Sheldon, Howard, and Raj — so much so that she even started gaming. Due to Penny and Sheldon's unique relationship, Sheldon taught Penny how to play an online computer game and it got her hooked.
Outside of gaming, the friendship between Sheldon and Penny was one of the best in the series. In season 2, Penny drove Sheldon to work, they got each other special Christmas gifts, he lent her money, and he helped create her own Penny Blossoms. Season 2 was just the start for these two.
Season 3: Howard's Hunt For A Girlfriend
Season 3's best storyline focused on Howard's hunt for love. After his attempts to woo Penny failed horrendously, he and Raj focused on other women.
Once the guys got back from the North Pole, Howard's desperation showed when he dressed as a goth to attract gothic women. When that didn't work, Howard begs Penny to set him up with a friend, which is when he found his future wife Bernadette. But before Howard matured and settled down, viewers got to see him as a jealous, emotional boyfriend who didn't know what he wanted.
Season 4: Leonard & Priya's Relationship Takeover
With Leonard and Penny's relationship timeline being a roller coaster, Leonard dove headfirst into a relationship with Raj's sister, Priya. Priya was the complete opposite of Penny and the two hit it off throughout season 4.
Seeing Leonard so happy with someone like Priya depressed Penny. The rest of the season left viewers wondering if Leonard and Priya were endgame and if Penny was ever going to tell Leonard that she still loved him.
Season 5: Amy's Inclusion Into The Group
Although Amy was introduced at the end of season 3 and made herself a fun part of the group in season 4, it wasn't until season 5 that Amy solidified herself as a best friend of Penny and Bernadette's.
It's in this season that Amy and Sheldon become official and she weaseled her way into everyone's hearts. She helped Penny get ready for a relationship do-over with Leonard, she helped Bernadette with her wedding, and she totally transformed over the years — with season 5 being the start of it all.
Season 6: Howard's Return From Space
Howard's journey into space at the end of season 5 was a big one for him, but the better storyline was in season 6 when he arrived back on Earth. Howard believed he was coming home a hero and that everyone would be dying to know about his experience. However, his loved ones became sick of his space stories that transpired throughout season 6.
More than that, he was no longer doing a once-in-a-lifetime thing; he was now back at home balancing life as a newlywed and dealing with his overbearing mom and bothered wife. It was a transition that was entertaining to watch.
Season 7: Penny's New Adventure
Season 7 was all about different work projects. From Professor Proton's paper to Amy's job at the university to Sheldon's issues with String Theory... But all eyes were on Penny.
Penny realized she lost control of her life and wanted to pursue acting full-time. After all, it didn't make sense for Penny to focus on waitressing over acting. Despite Leonard's worries, Penny quit her waitressing gig and went to more auditions. By the end of the season, Penny was working on a low-budget horror movie but at least she followed her dream.
Season 8: A Life Without Mrs. Wolowitz
In the middle of season 8, Howard received shocking news, his mother had died unexpectedly. Considering how close Howard and his mother were, this storyline was ongoing because of how much it affected Howard and his relationships.
Howard had to get her ashes from Florida and handle the home that she lived in. One of the saddest moments was the group eating the last meals she ever made.
Season 9: The End (And Beginning) Of Sheldon & Amy
At the end of season 8, Amy dropped a bombshell: she was breaking up with Sheldon. Their storyline took over season 9 because no one knew what would become of the former couple.
Amy was now best friends with Sheldon's best friends, this created awkward tension in the group. Things became even tenser when Amy started dating. Sheldon thought he was okay but he later realized a life without Amy wasn't what he wanted. Them getting back together later in the ninth season was one of the couple's most romantic moments.
Season 10: Moving Out & Moving On
Although Howard's Air Force project with the guys was an amazing storyline, the more transformative storyline was that among Sheldon, Leonard, Amy, and Penny. Sheldon was finally ready to move out of his safe zone and into Penny's old apartment with Amy. This was a learning curve for everyone.
Leonard and Penny were excited to live without Sheldon, but they also missed him. Sheldon also had to get used to living outside his comfort zone with a woman for the first time. This situation created multiple storylines and arcs throughout the season.
Season 11: Sheldon & Amy's Wedding
Although Bernadette's surprise pregnancy was a dramatic storyline in season 11, Sheldon and Amy's engagement and wedding overshadowed everything else.
Amy and Sheldon's relationship deemed itself perfect as they worked together (with the help of science) to create the perfect wedding. From dress picking to reception all searching — every detail was entertaining to watch. What's better is the scientific breakthrough that occurred for Amy and Sheldon at their wedding.
Season 12: The Theory That Became A Nobel Prize Winner
Raj's storyline with Anu was an intriguing one in season 12, but the idea of Amy and Sheldon receiving a Nobel prize was bigger. After 12 seasons of wondering if any of Sheldon's scientific theories were going to come to fruition, it finally happened and he was rewarded in the best way.
Watching Sheldon achieve his goals with his wife by his side, as they thank their best friends was the perfect ending to the series.