In just a few short weeks, we’ll know how The Big Bang Theory ends. The story of Sheldon, Leonard, Howard, Raj, Penny, Bernadette, and Amy – which could very well be the last really popular multi-cam sitcom ever made, with new developments in streaming and premium cable taking viewers away from broadcast television – will finally be over and we’ll see where they all end up.

Go back to any episode from the first season of The Big Bang Theory and you’ll see how vastly different the characters were then than they are now. Sheldon was a socially awkward genius who was completely indifferent to anyone. Leonard was a geeky nervous wreck who pined after the girl next door. Penny was a Cheesecake Factory waitress who dreamed of one day being a famous movie star. Howard was basically a sexual predator. Raj couldn’t speak to women. And Amy and Bernadette weren’t even there!

These characters are so completely different now than they were at the beginning of the series that they’ve basically become entirely new characters. So, as we head rapidly towards the series finale of The Big Bang Theory, here are 18 Major Ways The Characters Have Changed Since Season 1 (And 2 Differences That Make No Sense.)

Changed: Penny Is No Longer The “Girl Next Door”

Penny started off in season 1 as the most obvious example of the “girl next door” trope who had ever been created. She was the insanely attractive woman who lived literally next door to single loser Leonard, who spent the show’s early days pining after her.

Since sitcoms are designed for longevity, with characters who can supposedly stay the same for hundreds of episodes, it seemed like Penny would be the “girl next door” forever. But now, she’s moved across the hall to live with Leonard. A character who was once Leonard’s “girl next door” is now his live-in wife – she’s literally become the opposite of her initial characterization.

Changed: Howard Is A Family Man

At the beginning of the series, Howard was a pervert who would do anything to trick women into sleeping with him. He secretly filmed Penny while she was asleep and he created a robotic arm for, well, you know what. But now, he is a loving husband and father of two.

All of the characters have been through some tremendous changes on the show, but Howard has arguably matured the most. Sheldon has opened himself up emotionally, Leonard is more confident, and Raj is more independent, but Howard is a completely changed man. Put season 1 Howard and season 12 Howard next to each other and they’re chalk and cheese.

Changed: Leonard Is Married To Penny

This is one of the main changes from the show over the years. In season 1, Leonard hopelessly pined after Penny while she dated a bunch of douchey, muscular meatheads. Now, after a long on/off romance, the two have settled down together and tied the knot.

First, they eloped in Vegas, and later, after everyone kicked up a fuss for not being invited to their wedding, they had a nice ceremony in the park with all their friends and family in attendance. We got an answer to the age-old “Will they or won’t they?” sitcom question posed by the likes of Friends and How I Met Your Mother a lot earlier than we expected in The Big Bang Theory.

Changed: Raj Can Talk To Women

At the start of the series, Raj couldn’t even open his mouth when he was near a woman. Sometime in the early days of the show, he realized he could talk to women if he drank alcohol. But even then, that’s not a permanent solution. He couldn’t just get drunk all the time – you can’t develop a relationship like that.

Now, all these years later, he has no problem communicating with women and has revealed himself to be a hopeless romantic. Some of his closest friends are women. He’s built relationships with Penny, Amy, and Bernadette and spoken to all three of them enough that they’ve gotten to know him really well.

Changed: Sheldon’s In A Relationship With A Woman

In season 1, Sheldon wouldn’t have even considered the idea of dating. He was too focused on science and too out of touch with human emotion to have feelings for another person and a desire to see them romantically. But now, he’s in love! When he was first introduced to Amy, he still wasn’t ready for a relationship.

However, they spent some time together and, thanks to the fact she’s a scientist and very similar to Sheldon and also very, very desperate, they managed to strike up a relationship. Raj even pointed out how insane it was, at one point, that Sheldon Cooper found love before he did.

Changed: The Group Is Now Almost 50% Women

The cast of The Big Bang Theory has completely changed between season 1 and now. It went from being a show about four male geeks and their female neighbor to an ensemble piece like Friends with a near 50/50 split of men and women. Now, there are three men and three women just like Friends, with a person of color thrown in to make it slightly more diverse than Friends was.

It’s arguable that the show didn’t become really popular until it turned itself into Friends. The show about a bunch of nerds hanging out at a comic book store didn’t have ratings as high as the show about a bunch of nerds who somehow got girlfriends.

Changed: Howard’s Mother Passed Away

Although famously never seen, Mrs. Wolowitz was a well-rounded character of her own. She was introduced in the first season as Howard’s screechy, overbearing mother who always yelled at him so much that he lost his cool. These were among the show’s funniest scenes, and she became a beloved part of the show, despite never actually appearing on screen.

Sadly, the actress who voiced her, Carol Ann Susi, passed away a couple of years ago and, out of respect, the writers had the character pass away, too. This was a sad turn that no season 1 viewer would expect was coming later down the line. But of course, it’s something that couldn’t be predicted – or avoided.

Changed: Leonard Can String Together A Sentence

When we first met Leonard, he was a bumbling buffoon who could barely articulate himself. Now, he can actually string sentences together. It seems like a small difference, but the fact that he has changed his entire pattern of speech as he has become more confident and successful and fulfilled in his life.

It’s these kinds of little nuances in Johnny Galecki’s performance that have earned him nominations for a Primetime Emmy Award and a Golden Globe Award. At this point in the final season of the show, it’s not clear exactly how Leonard’s journey is going to end. Will it be a baby? Will he and Penny break up? We’ll just have to wait and see.

Changed: Sheldon Respects His Superiors

In season 1, Sheldon insulted his new boss and got himself fired. Now, he respects his superiors and studies the scientific fields he’s told to study and it’s done wonders for his career. He’s allowed to pursue his true passions now, which seem to be dark matter and his latest theory.

Frankly, if Sheldon hadn’t changed this about himself and started to be a team player at Caltech, he would’ve been fired a long time ago and stayed fired – and his mom wouldn’t have been able to get him his job back that time. So, it’s a good thing he finally grew up and began to respect the authority of his superiors at work.

Makes No Sense: Stuart Is Into Old Ladies

As we’ve seen from his very inappropriate relationship with Howard’s mother, comic book store owner Stuart has kind of a thing for old ladies. When we met him in season 2 (he didn’t appear in any season 1 episodes, but his store was mentioned in one episode,) he was an even bigger loser than the guys.

All he did was stand around lamenting the fact that no women came in the comic book store. At one point, he went on a date with Penny, but it would take a few years for us to find out what Stuart was really into. He and Mrs. Wolowitz really had something special, as unusual as it was.

Changed: Penny Grew Up

One of the biggest changes in the characters of The Big Bang Theory is simply that Penny grew up. She began in season 1 as a bright-eyed girl from Nebraska who worked as a waitress at the Cheesecake Factory and dreamed of being a movie star. Eventually, she got realistic about her goals for the future, and now, she has a prosperous career as a pharmaceutical rep.

There’s one fan theory that she can still make it as an actress by the finale, because Kevin Smith is a fan of hers. But as it stands, she’s a failed actress whose most popular work was the Serial Ape-ist franchise, but a very successful pharmaceutical rep.

Changed: Sheldon Moved Out

At the beginning of the series, Sheldon loved his apartment. He’d really made it his home, filling it with all his sci-fi memorabilia and taking immense proud in his spot on the couch. It seemed like he would just see roommates come and go. The previous guy, played by The Walking Dead’s Steven Yeun, warned Leonard against moving in with him, and Leonard was expected to warn the next guy.

However, now, Sheldon has moved out of the apartment and across the hall into Penny’s apartment with his wife Amy. He relinquished the apartment to Leonard and Penny, so they could enjoy marital bliss, and that’s something no one ever expected him to do.

Changed: Leonard Had A Shotgun Wedding In Vegas

If you went back in a time machine and told a Big Bang Theory fan watching the first season in its original airing that Leonard would one day elope with a woman in Las Vegas, they’d be very confused. He didn’t seem to be a Vegas guy at all. That's just not in Leonard’s wheelhouse.

If you wanted to confuse them even more, you could tell them the bride was Penny from across the hall, because that seemed like it would never happen. For Leonard to go from the spineless dweeb pining after Penny to the guy marrying her on a whim in Las Vegas is quite a transformation.

Changed: Sheldon Has Survived A Long-Distance Relationship

Long-distance relationships are tough for anyone, but especially when you have the social skills of Sheldon Cooper. And yet, when Amy was briefly relocated, he had to contend with the long-distance thing – and their relationship made it to the other side intact! In season 1, the guy would’ve struggled to keep up a short-distance relationship, let alone a long-distance one.

Most so-called “normal” people can’t make a long-distance relationship work, and yet somehow, when Amy went off to work at a university on the other side of the country, Sheldon managed to stay committed to her and keep her committed to him until she came back.

Changed: Howard Respects Women

Now that he has a wife and daughter, it’s fair to say that Howard has come to appreciate women as equals and human beings. But take a trip down memory lane back to a season 1 episode and you’ll see the character once had an astounding lack of respect for women.

He literally used a drone to spy on some sunbathing models and then crept into their house by pretending to be the cable guy. He filmed Penny while she was asleep and wore tattoo sleeves to trick goth girls into being interested in him. Now, as a husband and father, he’s finally learned to respect women.

Changed: Sheldon Appreciates His Friends

At the beginning of the series, it seemed like Sheldon saw his friends as a hindrance to his studies. Hanging around with them was a waste of his precious time. But now, he’s had some really emotional moments with all of them and he appreciates them as a valuable part of his life.

Remember the episode where all the characters tell Howard their version of what might be in his dad’s letter? Sheldon’s was so wonderful and heartfelt – a sign that he’d moved on from having no regard for Howard, or any of his other friends for that matter. And there’s been a bunch of moments like that over the years.

Changed: Howard Moved Out Of His Mother’s House

In season 1, Howard was still living with his mother. Frankly, back then, it seemed like he always would. He showed no signs of growing up, he wasn’t looking for places, and he seemed a little too dependent on his mother. Now, of course, he’s moved out and gotten his own place with his wife Bernadette, where they’re raising their children.

That’s quite a journey for a character who began as an adult man who still lived with his mother. With any luck, Howard’s own kids will move out of his house at a more appropriate time, although we won’t see that part of their lives.

Changed: Raj Handles His Own Finances, Sort Of

Raj used to have everything handed to him by his parents. Now, he has sort of grown up in the sense that he’s taken the responsibilities of his finances into his own hands. He immediately handed those responsibilities over to Sheldon, but at least his parents aren’t doing it for him anymore. That’s a start.

He isn’t completely independent anymore – he’s just independent from his parents. But that’s the first step towards growing up. We’ll likely be seeing more signs of Raj’s maturity by the time the series finale airs in May. That’s what his character development has all been about, ever since we were first introduced to his parents.

Changed: Howard Married One Of Penny’s Best Friends

In season 1, Howard was a loser who constantly tried to get Penny to sleep with him. She was disgusted by him and would hardly consider them to be friends. Cut to a decade later and he’s married to one of her closest friends. And it was all thanks to a pact Leonard and Howard made years ago that if one of them ever got a girlfriend, they would set the other one up with one of her friends.

So, Leonard reluctantly got Penny to set Howard up with one of her co-workers at the Cheesecake Factory, who happened to be a scientist. The rest, as they say, is history.

Makes No Sense: Howard Has Been To Space

The Howard we met in season 1 was an engineer who had access to the Mars Rover. Now, he has been to outer space and back. While this is a major difference for the character and he mentions it a lot, it never should’ve happened.

He failed the training, because he literally had to call his wife and his mother to both come down and comfort him after the first go at a physical test – there was no way NASA wouldn’t notice that and would still let him go to space. Plus, he’s deathly allergic to nuts, which are what most astronaut foods are made of.