1.Friends: There was a chance Jennifer Aniston wasn't going to get to play Rachel because of another pilot she was in, so while they shot the show's promo photos, she was asked to step out of a handful of them in case she didn't end up being in the show.
2.The Muppet Show: Most of the Muppets are left-handed. Why? Well, most puppeteers use their dominant (right) hand to work the puppet's mouth, which means they would use their left hand to move the puppet's left hand.
3.The Sopranos: Brett Wicks, who designed the logo for the show, originally thought The Sopranos was about singers, not mobsters. He felt it was important for the logo to "overcome any preconceptions that the name might imply," which probably explains the gun in the now iconic logo.
5.The Office: Phyllis Smith, who plays Phyllis Vance, was initially an assistant casting director for the show. But producers loved her so much while she was reading lines with actors during their auditions that she was offered the role.
6.The Flintstones: Pebbles was originally going to be a boy until a toy company said that a girl would make more money because they could sell Pebbles dolls. According to Flintstones creator Joseph Barbera, the dolls made around $3 million in the first two months.
9.Happy Days: Ron Howard accepted a role in the pilot of the show to avoid the Vietnam War draft. According to Howard, he had a horrible draft number (41 or 42), and, because the government wasn't accepting college deferment anymore — he had just been accepted into USC's School of Cinematic Arts — he needed a work deferment.
10.A Different World: To keep the show authentic and relevant, producer/director Debbie Allen, who went to Howard University, took the writing staff on field trips to Morehouse College and Spelman College in Atlanta so they could actually experience and understand historically black colleges.
11.The X-Files: To compensate for the 10-inch height difference between David Duchovny and Gillian Anderson, Anderson often stood on a box during scenes.
13.Saturday Night Live: Jim Carrey auditioned to be a cast member multiple times, but was never hired.
14.I Love Lucy: When the show first aired, it was sponsored by Philip Morris cigarettes...which is one of the reasons why Lucy, Desi, Ethel, and Fred were always smoking.
15.Cheers: Ted Danson actually went to two weeks of bartending school to prepare for his role as Sam.
16.Frasier: Kelsey Grammer was the first actor to be nominated for an Emmy for the same character on three different series: Frasier, Cheers, and Wings.
17.Seinfeld: The show's composer slightly tweaked the opening theme music for every new episode.
18.Breaking Bad: When you combine the titles of Season 2's first, fourth, tenth, and thirteenth episodes you get "Seven Thirty-Seven, Down, Over, ABQ," which is a foreshadowing of the plane crash at the end of the season.
19.Mad Men: It was the first basic-cable show to be nominated for Best Drama, alongside Damages.
20.Sex and the City: If you look closely, you'll notice there's a continuity error in the opening sequence. The bus that splashes Carrie is full of passengers, but after the bus passes, the people have magically disappeared.
21.The Simpsons: Homer's catchphrase "D'oh" is written as "annoyed grunt" in the scripts.
22.Married... With Children (and Modern Family): Ed O'Neill's characters on both shows can be seen reading the same newspaper.
23.Parks and Recreation: Chris Pratt was not originally supposed to be a series regular, but he was so great as Andy that the writers created a bigger role for him.
24.Family Matters: The infamous theme song "As Days Go By" wasn't always the theme song. "What A Wonderful World" was used in the pilot (though it has been replaced with "As Days Go By" in syndicated versions of the show).
25.Full House: Dave Coulier stole Joey's iconic "Cut. It. Out." line from his friend Mark Cendrowski, who directs The Big Bang Theory. According to Coulier, to this day, Cendrowski says, "You owe me money for that."
26.The Mary Tyler Moore Show: Valerie Harper almost didn't get the part of Rhoda because she was too "attractive." Apparently the producers had someone more "unkempt" in mind.
27.The Jeffersons: For two years, Marla Gibbs, who played Florence, kept her job at United Airlines in customer service while simultaneously filming for the show. Sometimes people would recognize her voice over the phone.
28.The Brady Bunch: Uh, you might have noticed that the kids' bathroom didn't have a toilet. Allegedly, network censors at the time didn't want a toilet shown on TV.
29.The West Wing: The longest "walk and talk" scene the show ever shot was three minutes long, took half the night to shoot, and involved around 500 extras.
30.Arrested Development: Tobias's mustache was almost a no-go on the show because apparently FOX has a "no facial hair, no ball caps, no puffy sleeves" motto for men.
32.30 Rock: Donald Glover wrote the infamous "Werewolf Bar Mitzvah" song.
33.Gilmore Girls: Those town-meeting scenes often took full 20-hour days to film because of all the characters' reaction shots. They would sometimes play games to make the time go by.
34.House: Lin-Manuel Miranda was in two episodes of the show. He played Dr. House's roommate in a psych ward.
35.That '70s Show: Mila Kunis lied about her age at her audition. They were looking for actors 18 or older to work around hour restrictions for minors, and, at the time, she was only 14.
36.Everybody Loves Raymond: Jane Sibbett (who played Carol on Friends) was originally offered the role of Debra, and Maggie Wheeler (who played Janice on Friends) auditioned for the role of Debra before ending up as Debra's friend Linda.
37.How I Met Your Mother: Lyndsy Fonseca and David Henrie, who played Ted's kids, had to shoot all of their scenes during Season 1 to work around the fact that Henrie was going through puberty. Therefore, they had to keep the secret about the show's ending for nine years.