Friends may be one of the most entertaining sitcoms of all time, but it wasn't without its flaws. Over its 10 seasons and 236 episodes, there were plenty of continuity errors. Even with reruns airing on multiple channels every day, DVD and Blu-ray sets and the series streaming on Netflix, fans can't catch every one.

Most of the mistakes found are easy to explain. Television shows do multiple takes of scenes. In editing, sometimes those takes are put together to make the final version that you see in the episode. That can lead to continuity errors with props, wardrobe or characters' placements.

However, mistakes like that shouldn't be in the final product. Someone should have seen them in editing, especially in the case of a different piece of clothing, liquid in a glass or a missing prop. In at least one instance, it could simply be things change after the pilot episode. In another case, it's a matter of a set being visible because part of an apartment is simply never in the show and therefore wasn't built.

However, fans don't always catch mistakes like this because they're focused on the plot and the characters. Friends benefited from this because it featured 10 seasons of entertaining, humorous episodes. Some of these errors are easy to catch upon a second or third viewing of an episode.

Still, fans likely didn't notice them the first time they watched or unless they paused or rewound a scene. They were often too minor to catch viewers' eyes right away.

Here are the 30 Mistakes Fans Completely Missed In Friends.

Paul Couldn't Have Used the Stairs to Leave Monica's Building

Friends Season 1 Episode 1 Paul Leaving

In the pilot, Monica led Paul out of her apartment after he spent the night. Rachel, Chandler and Joey watched her say goodbye to him in the doorway. As she turned to walk back inside, he walked off to the right. However, he should have walked to the left to get to the stairs and leave the building.

Sure, there could have been another staircase, but why would there be another one close enough to use it?

The simple explanation is this was the pilot, and they didn't realize the building's layout yet.

Paper Towels Rolled and Unrolled

Friends Season 1 Episode 12 Paper Towels

Phoebe told Rachel Paolo made a pass at her in season 1 episode 12. Rachel was upset that Paolo played her and grabbed a paper towel from the roll hanging in the kitchen. However, instead of just tearing one off, she pulled the roll with her, so it stretched across the kitchen.

The two women both apologized before realizing Paolo was the one at fault. Rachel then sat at the table, wondering how she didn't see it, and still holding the paper towel. However, the paper towels went from being unrolled to rolled behind her in the kitchen.

The Disappearing Table

Friends Season 1 Episode 19 Table

In season 1 episode 19, Rachel was watching Marcel when the monkey ran away. As she told Ross what happened, fans saw the monkey was outside on the terrace. They also saw that there was a table inside the apartment, under the picture hanging near the front door.

However, when animal control showed up about a minute later, Rachel let the woman into the apartment. As she did, you could see the picture near the door — and there wasn't a table under it. What happened to that table in such a short period of time while Rachel and Ross were busy arguing about Marcel? They wouldn't have had time—or reason—to move it.

The Moving Mugs

Friends Season 2 Episode 4 Mugs

Rachel was clearing mugs from tables when Ross asked for advice about his relationship in season 2 episode 4. He and Julie hadn't been intimate yet.

When he sat down in a chair, the red mug on the tray on the counter was closest to him.

However, as Rachel gave him advice, the mugs changed positions on the counter. The smaller, green mug was closer to Ross, and the red mug was behind it and to the right. The red and green mugs switched places as Rachel advised him to wait to be with Julie.

The Disappearing Necklace

Friends Season 2 Episode 7 Necklace

Rachel was wearing a necklace as she worked in Central Perk in season 2 episode 7. She had it on as she spoke with Monica, Chandler and Joey about Ross and Julie.

Ross and Julie then joined the others and announced they were getting a cat. Rachel wasn't wearing a necklace during her initial reaction to the news. However, the necklace reappeared as she continued to question the couple getting a pet. It then disappeared again after Julie explained how she and Ross would split custody. It didn't reappear again during the scene.

A Visible Set

Friends Season 2 Episode 20 Visible Set

In season 2 episode 20, Richard was playing foosball with Chandler and Joey in their apartment. Behind him and over his right shoulder, you could see the door. That means to his left, the apartment should have continued.

However, as the camera panned as he asked, "could that shot be any prettier?" the fact that it was a set was obvious. You could see the end of the wall and the hallway behind it where the wall should have continued to wrap around. That was the part of the apartment you pretty much never saw—and obviously was never built.

The Stain Changed Sizes

Friends Season 3 Episode 2 Hummus Stain

Phoebe got hummus on her dress while everyone was getting ready for Ross' event in season 3 episode 2.

Throughout the episode, the stain changed sizes.

At times, it looked like she cleaned off the hummus or tried to, at least. It was significantly smaller as Monica checked her message on Richard's machine. However, it then reverted back to the giant stain it was when it first happened immediately after. It stayed like that until Phoebe put a giant Christmas ribbon on her dress in an attempt to cover it.

The Door Went from Open to Shut

Friends Season 3 Episode 13 Open Door

Monica and Richard pretended they could just be friends and she helped him cook in season 3 episode 13. As they squished tomatoes in a bowl, the doors to Monica and Rachel's bedrooms were both wide open in the background.

Richard got tomato on his shirt, and Monica helped him start to clean it off. Both doors were still wide open. However, suddenly Monica's door was closed as they realized they were in each other's personal space. It remained closed as Monica backed away and alerted him to the tomato on his pants.

The Suits Switched Hands

Friends Season 3 Episode 21 Ross Suits

In season 3 episode 21, Ross had a TV appearance and didn't know which suit to wear. He showed his two options — a blue suit or a brown suit — to Joey and Chandler. When he took the suits out of the carrying bag, he held the blue one in his left and the brown in his right, with the bag tucked under his right arm.

Then, before the scene ended, the blue suit was in his right hand and he was holding the bag behind it and the brown one was in his left. It would've been impossible for him to juggle the suits in such a short period of time.

The Guitar Disappeared

Friends Season 4 Episode 7 Phoebe Guitar

Ross offered Phoebe musical advice while she played guitar in season 4 episode 7. She held her guitar in her hands as she listened to him. She was still holding her guitar as he spoke about his musical past and finding his "sound." Phoebe asked him to play for her, and he refused.

Suddenly, her guitar was gone as she encouraged him to play.

He again protested briefly, but then he agreed to — and Phoebe was once again holding her guitar. She didn't have enough time to put it down and pick it up again.

The Glass Emptied and Filled Itself

Friends Season 4 Episode 14 Monica Orange Juice

Monica poured herself nearly a full glass of orange juice in season 4 episode 14. She put it down to feel what Phoebe thought was a baby kicking. She was holding it when Joey hurried past her and Rachel to get to set on time. The glass was closer to half full.

There was more juice in the glass as Monica asked Rachel how her date with Joshua went. When Rachel said she didn't see Joshua, the glass was less than half full. Monica never even made an attempt to look like she took a sip. As Rachel continued talking about her night, the glass was suddenly almost full again.

The Writing on the Magna Doodle Changed

Friends Season 4 Episode 20 Magna Doodle Writing

The writing on the magna doodle kept changing during one scene in season 4 episode 20. First, as Joey complained about staying up all night before a sleep clinic, "get out" was on it. It stayed on there as Rachel talked about Ross and Emily's wedding.

However, the writing changed to "poop" as Chandler talked about how he didn't dance at weddings. Ross then walked in as Chandler was showing Rachel and Joey how he danced. The magna doodle then read "get out" again as Ross told them his and Emily's wedding date.

A Sock Appeared on Monica's Hand As She Knocked on Her Door

Friends Season 5 Episode 2 Monica Hand Sock

Rachel asked Monica to make decisions about her love life in season 5 episode 2. When Monica didn't want her to tell Ross how she felt about him, however, Rachel locked her out. Monica began knocking on her door, bare-handed, demanding she let her in.

Ross was the one to open the door for Monica. When he did, there was suddenly a sock on her right hand, raised to knock again.

However, just before that, she'd been hitting the door still bare-handed, with her left hand. She had time to switch hands. She didn't have time to move her laundry basket to the other side and put a sock on her hand.

3D Glasses Disappeared from Phoebe's Hand

Friends Season 5 Episode 13 3D Glasses

Phoebe's grandmother's funeral was in season 5 episode 13. When the others joined Phoebe, she held several pairs of 3D glasses in her hand. She gave one to the man who introduced himself as Frank Buffay.

After she reacted to his name, he took it back and gave her the glasses before leaving. She held 3D glasses in both hands. The others joined her as she realized who he was. As she told them the man was her father, the glasses in her right hand were gone. They never appeared again during the scene, before or after the commercial break.

Joey Changed Shirts On-screen

Friends Season 5 Episode 17 Joey Shirt

Joey spotted an "attractive girl" in Ross' building across from Monica's in season 5 episode 17. He was wearing a black shirt as he did. He then ran across to the other building to try to find her, and he was wearing a purple shirt. He could've stopped to change shirts, so that wasn't a problem.

However, his shirt was black again as he knocked and Ross opened the door. It changed between a wide and close shot of Joey leaning in the doorway. It was obvious they used two different takes and messed up his wardrobe.

The Red Slider on the Magna Doodle Changed Sides

Friends Season 6 Episode 11 Magna Doodle Slider

Joey and Janine and Monica and Chandler tried double-dating in season 6 episode 11.

When Joey and Janine entered their apartment after one of their attempts, the red slider on the magna doodle was on the right side.

Janine didn't like the other couple, and they heard her complaint. Monica and Chandler stormed in to confront her. Joey told them to go home so he could talk to his roommate. When he closed the door after they left, the red slider was on the left side of the magna doodle. No one could have moved it.

On Which Side Was the Firefighter Holding His Helmet?

Friends Season 6 Episode 18 Firefighter Helmet

There was a fire in Phoebe and Rachel's apartment in season 6 episode 18. Monica, Chandler and Joey went with them to see the damage. The firefighter they spoke with held his helmet with his right hand, under his arm, when they walked in. He kept holding it on his right side as the friends discussed what happened.

Then, he walked back over to them, and his left hand was hanging down his side by the rest of his equipment. Suddenly, when the camera focused on him again, the helmet was under his left arm. He didn't have time to switch it.

A Water Bottle Disappeared from and Reappeared in Ross' Hand

Friends Season 6 Episode 18 Ross Bottle

Ross was holding a water bottle while Joey and Chandler spoke about a favor in season 6 episode 18. Ross drank from and was visibly holding the bottle during their conversation about someone from his and Chandler's college. However, he thought they were discussing someone else.

As he realized he was thinking about someone with the same first name, the water bottle suddenly disappeared from his hand. He couldn't have set it down behind him off-screen, because he was standing in front of the stove and sink. Then, as Monica interjected in the conversation, Ross was holding the water bottle again.

The Text of the Engagement Announcement Was Repetitive

Friends Season 7 Episode 5 Engagement Announcement

Monica and Chandler were engaged in season 7. In episode 5, they had an announcement printed in the newspaper. It had a photo of Monica and Joey, since Chandler wasn't photogenic.

Pausing on the announcement reveals it repeated several lines.

In fact, the repetition began with the last word of one sentence ("missed"). It continued until the end of the column, which ended mid-word on "century" with "ce." There was also a grammatical error in the text. It read, "the Geller's are personally overseeing." It should have read "the Gellers," plural not possessive.

The Magna Doodle Pen Changed Positions

Friends Season 7 Episode 11 Magna Doodle Pen

As Rachel enjoyed cheesecake in her and Joey's apartment, the magna doodle pen was hanging down in season 7 episode 11. Chandler walked in, and the pen swung as he opened the door. However, when he closed the door, the pen was on the magna doodle, in its holder.

He didn't have enough time to put it in its holder. He also didn't make any motions that would have explained the change in placement for the pen. The pen was once again hanging down from the magna doodle when he walked out of the apartment.