In 2006, The Big Bang Theory creators, Chuck Lorre and Bill Prady, shared their idea for the show with executives but the pilot was turned down immediately by networks. According to Cheat Sheet, the show had to be either heavily rewritten or scrapped entirely. With a pilot like this, it was bound to be skipped by viewers. In the unaired pilot, TBBT still had Leonard and Sheldon as the stars but everything else was different.

The pilot that was scrapped had a much darker tone. With Sheldon and Leonard still being geniuses who lived together, they also lived a very lonely life. The unaired Big Bang Theory pilot revolved around them meeting and helping a young woman who was down on her luck. But unlike the Penny that fans grew to love, this character was Penny's polar opposite. The extreme differences in the unaired pilot made fans appreciate the aired pilot so much more.

Updated on May 9th, 2022, by Lynn Gibbs: It's hard to imagine The Big Bang Theory without the connection between Penny, Leonard, and Sheldon, but in the original, unaired Big Bang Theory pilot, that's where the show was heading. When the original pilot was filmed, there was no Penny, Raj, or Howard. Sheldon and Leonard remained the main characters with a very different life than the ones fans grew to love over 12 seasons. Luckily, the creators made some tweaks, and a lighter, funnier, and smarter version of TBBT was created. 

Sheldon Noted What He Liked Most About A Woman's Body

Sheldon and Leonard in the sperm bank on TBBT

The Sheldon Cooper that fans came to know was completely uninterested in sex and romance. He was not entertained by women in the slightest and was much more a man of the mind. But that wasn't how he was written in the unaired pilot.

RELATED: 10 Of The Most Skipped The Big Bang Theory Episodes, According To Reddit

The unaired episode started with Sheldon and Leonard at the sperm bank (just like in the aired pilot), but when Leonard joked around about Sheldon's preferences in women, Sheldon said, "Fortunately, I stumbled across a magazine that featured women with large buttocks." Sheldon said plenty of off-beat quotes in the unaired pilot but this was by far the most uncharacteristic.

There Was No Penny

Leonard and Sheldon first meet Penny

Leonard and Penny's relationship timeline was a major subplot throughout TBBT. But in the unaired pilot, Penny was not a character and Kaley Cuoco was not cast. Cinema Blend agreed that it's hard to imagine TBBT without Penny, but in her place was a woman named Katie.

Katie was introduced while Sheldon and Leonard are walking home from the sperm bank and found her crying on the curb. She was blonde like Penny but that's all the two had in common. It became clear that from then on the show would have focused on Sheldon, Leonard, and Katie.

Katie Was Edgier & Angrier

Katie sitting on the ground judging Sheldon and Leonard on TBBT

When fans met Penny, she was bubbly, happy, and genuinely interested in Sheldon and Leonard's brilliance. She was in awe of her new neighbors and appreciated their company. Katie, on the other hand, was a darker character.

According to the unaired pilot's Fandom page, Katie was a "tough-as-nails" character. She judged Leonard and Sheldon upon meeting them and was irritated by them. The only reason she hung around them in this episode was because Leonard offered to buy her dinner. While some fans had unpopular opinions of Penny, watching Katie's angry personality made fans miss Penny all the more.

Katie & Leonard Didn't Have The Same Loving Connection Penny & Leonard Had

Penny and Leonard about to kiss in The Big Bang Theory

Even in the pilot, fans felt the connection between Leonard and Penny. Even though they were shown as opposites, there was a blurry indication that Penny and Leonard would have feelings for each other down the road.

RELATED: Leonard & Penny's Relationship Timeline In TBBT, Season By Season

In the unaired pilot, however, that same mutual connection was not felt between Leonard and Katie. It was obviously Leonard had a crush on Katie because she was a beautiful woman in need of help, but Katie only used Leonard for a place to stay and for food. The bond between Leonard and Penny was more fun to watch.

Sheldon Was Around Naked Women Before Amy

A split image of Sheldon eating food with Katie and Leonard and later standing in the laundry room with Penny on TBBT

Not only did Sheldon admit to liking the backsides of women, but he also admitted to Katie that he saw a total of "six women naked."

While at dinner, Katie judged the guys' social status and asked Sheldon if he's ever "seen a lady naked." Sheldon was silent for a while before admitting, "I have seen six women naked." In the show that fans know, Sheldon never had sex until his relationship timeline with Amy began. It's one of the things that made him and Amy so close.

Katie's Boyfriend Wasn't Longterm Like Penny's Was

A split image of Sheldon and Leonard approaching Katie on the street and later with Kurt in TBBT

One of the saddest things about Penny upon meeting her was that she had just gotten out of a relationship with a guy that she had been with for four years. The apartment across the hall from Sheldon and Leonard was Penny's first act of independence.

In a clip from the unaired pilot, Katie had also just gotten out of a relationship, but it wasn't the same length as Penny's. Katie told Leonard and Sheldon that she found out her boyfriend had a wife, which was far more complicated.

Sheldon & Leonard Had A Spare Bedroom!

A split image of Sheldon and Katie in his living room in the unaired pilot next to the gang eating dinner in his apartment on TBBT

Leonard and Sheldon's apartment was the main location in the aired version of TBBT. Between apartment 4A and apartment 4B, Sheldon and Leonard's apartment had the best scenes and was a place where everyone came together and conversed.

The apartment shown in the unaired version, however, was completely different. It was darker and smaller. There even appeared to be a fireplace with Sheldon's whiteboard resting on top of it. A smaller and darker apartment wouldn't have made sense for weekly dinners with 7+ people.

Meet Gilda!

A split image of Gilda and Leonard from the unaired version of TBBT next to Leslie Winkle

In the version of TBBT that fans loved, the one female friend that Leonard and the gang had at work was Leslie Winkle. She worked in the same department as Leonard and later had chemistry with both Leonard and Howard.

In the unaired version, a clip showed another female colleague, a scientist named Gilda. Gilda spoke the same scientific language that Sheldon and Leonard did and seemed threatened by Katie's intrusion into the group. Instead of a romance between Leonard and Katie, it seemed like a relationship with Gilda was more plausible.

Sheldon Was Sexually Experienced

A split image of Gilda from the unaired pilot of TBBT and Sheldon sleeping with Amy

Sheldon wasn't one to think much about women or sexuality in TBBT. He only began having those feelings once he met Amy. However, in a clip from the unaired pilot, it was said that Sheldon was sexually active.

RELATED: Sheldon & Amy's Relationship Timeline In TBBT, Season By Season

Gilda told Leonard that she and Sheldon had slept together, which Sheldon wanted to keep on the down-low. It didn't make sense to die-hard fans that Sheldon would causally sleep around because it went against his character, but that's the difference between the unaired and aired pilot.

Where Were Raj And Howard?

Raj and Howard standing in awe on The Big Bang Theory

One of the biggest differences in the unaired pilot was how lonely Sheldon, Leonard, and Gilda seem to be. Their apartment was dark, they had little friends, and they appeared desperate for some life.

More than that, Howard and Raj were nowhere to be found in the unaired pilot. The focus on friendship was a large theme throughout TBBT, and it was interesting to picture the series without Penny, Raj, and Howard to lift the spirits of Leonard and Sheldon. Without Howard and Raj, the show wouldn't have had the same humor or depth.

Sheldon Went To Bars And Drank Alcohol

A split image of Sheldon drinking a beer in the unaired pilot of TBBT and later a still of Sheldon ordering a coke

At the end of the unaired pilot, Sheldon, Leonard, and Gilda went to a bar with Katie to let off some steam. Knowing Sheldon from the aired series, watching him go out and party could have killed the show in itself.

It's so unlike his character that it's hard to picture Sheldon casually drinking a beer and dancing on a dance floor with his friends. Nevertheless, this was the old Sheldon. The Sheldon that fans know today would never release steam like that unless he was incredibly heartbroken — or in the name of science.

NEXT: 10 Controversies That Almost Killed The Big Bang Theory