Living in Apartment 4b, Penny had the opportunity to move in across the hall from Sheldon and Leonard. At the young age of 22, she didn't realize that the shy, geeky guy across the hall would later become her husband.

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Although Penny spent many nights at Leonard and Sheldon's apartment (due to them having WiFi and dinner), she also adored her apartment across the hall. Since she couldn't paint the walls, she made her space her own by adding bright colored decorations and furniture to add a little Penny to an otherwise dark apartment. And while many fans laugh at the fact that there was no way Penny could ever afford an apartment of that size on her own (by only working a few shifts at the Cheesecake Factory), we're taking a look at some things fans may have missed.

SHE HAS PICTURES OF THE CAST ADN CREW ON HER FRIDGE

If you take a closer look at Penny's fridge the next time you're binge-watching The Big Bang Theory, you may notice a few familiar faces.

The pictures on the fridge are real photos of Kaley Cuoco, the crew, and a few of herself, Melissa Rauch (Bernadette), and Mayim Bialik (Amy Farrah-Fowler)!

WE'VE ONLY SEEN THE WALL BEHIND PENNY'S TV ONCE

amy and penny picture - bbt

Thanks to our view of Penny's apartment, we never see the wall that the couch is facing. The "wall" is where the cameras are and gives us a better view of what's going on in the scene. It's assumed that the wall that the couch is facing is where her TV is.

But once Amy and Penny became BFFs, Amy decided to celebrate their friendship by getting an oil painting done of them. The painting was so large and ugly, the only space available to hang the portrait was (presumably) above her TV. The cameras panned to the entertainment wall that one time to get a better view of the portrait and that was it.

FIRST EPISODE BLUNDERS

When we first see Leonard's view of Penny for the first time, she's moving into the apartment across the hall. Leonard is transfixed on the beautiful blonde and can't help it but introduce himself to her.

When the camera zooms over to Penny though, her apartment's design is a hair out of place. When we look into Penny's apartment, we can typically see her living room and the kitchen, but in this scene, the kitchen isn't in the view at all.

WHERE DOES THIS WINDOW LOOK OUT TO?

When we take a look at Penny's bedroom, it can be hard to visualize how the rest of her apartment is situated. The window on the left side of the picture faces the same view that we see when Penny is sitting at her cute dining table.

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But what about this window next to her bathroom door? We know the window is real because Sheldon comments on it when him and Amy are doing their trial stay, but the window's curtain has never been drawn back. This makes it difficult to visualize what her view would be like from that window since we always picture it being another wall to her room.

WHAT'S UP WITH THE KITCHEN WINDOW?

It's hard to imagine a scene where Penny had her kitchen window open. For starters, many fans thought Penny's kitchen window was fake due to her fake picture of palm trees on it. Kind of like the "fake" window in her room next to her bathroom.

However, when Amy and Sheldon move into Penny's apartment, Amy has the kitchen window open!

WHERE IS HER APARTMENT COMPLEX LOCATED ANYWAY?

Both Penny and Leonard's apartments are on the fourth floor — the only two on the fourth floor, in fact. However, their address and general direction from different areas of interest seem to change.

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In the earlier seasons, we learn that the address of their apartment complex is 2311 North Los Robles Avenue. That address seems to differ in season five when it's said to be located at 215 South Madison Avenue. Funny enough, when you place both addresses into Google Maps, the two addresses are just a nine-minute drive from one another. However, that doesn't seem to answer where Penny actually lives...

WE CAUGHT A GLIMPSE OF HER TV TWO TIMES

The specific view in the picture above is a rarity. The camera is often in the same position as Penny's entertainment area but in this view, we can actually see her entertainment center.

Another time where this happened in the show is when Penny invites friends over to watch the Nebraska game when she and Leonard are newly dating. Other than that, we never see her TV.

WHY DOES SHELDON KNOCK IF THERE'S A DOORBELL?

Diehard fans know the real reason why Sheldon knocks three times before entering a room (he once walked in on his father and another woman), but why does he still knock when there's a perfectly good doorbell that does the same job?

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Doorbells are actually louder at times and more attention-grabbing. Funnily enough, Leonard and Sheldon's apartment also has a doorbell and even Penny continues to knock!

HER BATHROOM MIRROR APPEARED OUT OF NOWHERE

In season three's "The Adhesive Duck Deficiency," Sheldon comes to Penny's rescue after she slipped and fell in the shower. He helps her up and gets her dressed before heading to the emergency room.

The picture on the left is a cropped image of that scene where there is no bathroom mirror above her sink, just a picture. In the scene on the right, a bathroom mirror suddenly appears and is her sink now baby blue instead of the previous white?

AND THIS CHAIR TRANSITIONED TO HER BEDROOM

Penny's apartment decor has a '70s vibe to it, filled with bright colors and fun patterns. In the episode "The Middle Earth Paradigm", Penny throws a Halloween party at her apartment with a bunch of friends she somehow loses as the series goes on... Nevertheless, we see a bright green Skruvsta Swivel Chair that was once in her living room.

Over time, the chair disappeared and she found a new one that Sheldon was comfortable with, but the chair later pops up again in Penny's bedroom! In real life, fans can actually buy the chair from IKEA!

NEXT: Big Bang Theory: Every Main Character, Ranked By Intelligence