As expected, the sitcom left fans off with a 'big bang' of its own during the final episode. Wrapping up the series, The Big Bang Theory ended things off on a strong note, with critics and fans praising the last episode.

However, as we're going to reveal in the following, there was a certain storyline fans weren't exactly thrilled about, and the same held true for the stars of the show, Johnny Galecki and Kaley Cuoco.

We're going to reveal which storyline those on Reddit deemed as the most controversial, while also highlighting how Galecki and Cuoco felt about it. Clearly, the two stars wanted things to go in a different direction, and were surprised by the way things played out.

Fans On Reddit Voted Penny's Pregnancy As The Most Controversial Storyline On The Big Bang Theory

During its 12 season run, it was inevitable that The Big Bang Theory would run into some questionable storylines. According to Startefacts, those on Reddit deemed the Penny pregnancy storyline as they most controversial of all the plots throughout the series. It especially stirred things up given that it seemed as though Penny and Leonard were content without having children. Certain fans weren't pleased that the creators went back on this during the final season.

In truth, Chuck Lorre revealed in The Big Bang Theory: The Definitive, Inside Story of the Epic Hit Series, that Penny's character was very underwritten throughout the show, and this might've been another example.

"One of the most underwritten characters in the show early on was Penny. It was really obvious immediately that we hadn't developed the character beyond the pretty girl next door, and Kaley was certainly capable of doing a great deal more than what was asked of her. We had to make the character more fully realized. "

Without a doubt, Penny made a major contribution to the series. However, the man behind Leonard, Johnny Galecki wasn't pleased with her conclusion in their relationship.

Johnny Galecki Was Shocked By The Pregnancy Twist, And Didn't Get It

For the most part, the cast of The Big Bang Theory cast were content with the finale, and the same held true with the fans and critics. The final episode received the highest rating on IMDb. Fans especially adored Sheldon's send-off, and his emotional speech following the Nobel Prize victory.

However, the same didn't hold true for Johnny Galecki. The actor revealed alongside The Hollywood Reporter to being taken aback after reading the script.

"The pregnancy shocked me. I didn't get it at first. Molaro and I talked about them maybe not [being pregnant].

Ultimately, Galecki came to terms with the finale, given that it ensured everyone was going to be okay.

"The main takeaway is that these friendships will continue; the writers didn't want someone to move away. We wanted to leave the audience with the idea that these friendships and the love that they have continues."

Similar to Johnny Galecki, Kaley Cuoco also took issue to Leonard and Penny's future, wanting things to shape out differently for the couple.

Kaley Cuoco Would've Rather Penny Didn't Get Pregnant And Stuck To Her Principles

Kaley Cuoco would've rather Penny and Leonard did not opt for children. According to Cuoco, she liked the message Penny was sending throughout the series about not having children.

She revealed, "I actually wished that they did not [make Penny pregnant], because I loved that message [of Penny not wanting kids] so much. It was cute how the writers did it at the end with Penny's surprise pregnancy, and all in all I'm glad, but I was actually voting for her not to [get pregnant]."

However, it seems like Cuoco came to terms with the storyline later on, accepting the circumstances, and Penny's future.

"I was super happy. I didn't expect it at all because they've been playing against it for so long. I thought they did it so well and loved how it was a surprise and she was wrapping her brain around it. I think they're going to be awesome parents. They waited so many years, and they're so fun and easygoing. Or Penny is really kind of easygoing! I think they'd be adorable parents. I can only imagine," she tells The Hollywood Reporter.

Although it was a concerning moment for fans, the finale was strongly praised, in large part, given that it didn't give the fans a notion that the friends would be splitting up and going their own ways.

The creators and writers did a great job in ensuring that everything was going to be the same, and the group would still be close together. At the very least, that is what the pregnancy storyline accomplished, while also honoring Leonard's words from the pilot episode.