We're living in the golden age of TV. No longer is it seen as an inferior medium to cinema or poor man's entertainment, and many actors would rather have a role on a successful show than a big-budget movie nowadays. As such, the competition is now fiercer for roles, and everyone wants in on the meaty parts.

The late comedian Milton Berle once said, "If opportunity doesn't knock, build a door"-- and he's completely right. However, when it comes to TV, the industry is known for building high walls for a variety of stupid and inexplicable reasons. On the other side of the coin, though, some actors create their own obstacles and sabotage their careers in the process.

Throughout the years, we've found out about mainstream roles that could've been played by someone else. However, it's intriguing to dig a bit deeper at some of the reasons for these actors not getting the parts. In several instances, the logic is mindbogglingly strange, and goes to show that this industry isn't based purely on talent or star power but other agendas.

So, let's take a gander at the 15 Actors Who Lost Out On Big TV Roles For Mind-Blowing Reasons.

Katie Holmes

Katie Holmes as Buffy Summers in Buffy the Vampire Slayer

It's hard to imagine anyone else besides Sarah Michelle Gellar as Buffy Summers (even if Kristy Swanson was the first to portray the character in the 1992 movie), but we nearly had a different lead actress in Joss Whedon's Buffy the Vampire Slayer TV series.

When castings took place for the show, Katie Holmes was reportedly offered the lead role. However, she turned it down in favor of finishing high school. A year later, Holmes auditioned for the part of Joey Potter in Dawson's Creek and got it.

In retrospect, things turned out okay for both Gellar and Holmes, as they were important parts of their respective and acclaimed shows. In 2006, Holmes finally got her vampire fix by marrying Tom Cruise, who is unquestionably a daywalker.

Olivia Wilde

Olivia Wilde as Marissa Cooper in The OC

Out of the actors who appeared on the teen drama The O.C., it's the supporting characters who've gone on to become the biggest successes in Hollywood – most notably Olivia Wilde. However, things could've been a lot different for Wilde had she gotten the role she originally auditioned for: Marissa Cooper.

Josh Schwartz, the creator of the show, explained how the casting for the lead role came down to Wilde and Mischa Barton. He believed that the character needed a vulnerability, and Wilde was too empowered to portray a broken teenager.

According to him, "Olivia Wilde needed no saving." Despite not getting the part, Wilde did appear in season two as Marissa's girlfriend, Alex Kelly.

Barton left the show at the end of the third season, and the popular drama didn't last too long afterwards.

Thomas Jane

Thomas Jane as Don Draper in Mad Men

It's difficult to imagine anyone else but Jon "Bruce Wayne" Hamm as the dapper Don Draper in Mad Men. As Hamm explained on WTF with Marc Maron, though, he was never the first choice for the part.

"I started, literally, on the very, very bottom. I couldn't have had less heat on me. Nobody knew who I was. The casting directors didn't know who I was. I wasn't on anybody's lists. The funny thing was, I think they went to Thomas Jane for it, and they were told that Thomas Jane does not do television," he said.

Well, Jane eventually sucked up his pride and appeared in the HBO series Hung from 2009 to 2011. His performance as Ray Drecker was well-received by critics and fans, but he never won a Golden Globe – unlike Hamm, who scored one for his role in Mad Men. Touché.

Sandra Bernhard

Sandra Bernhard as Miranda Hobbes in Sex and the City

Comedian and actress Sandra Bernhard has appeared in a variety of movies and TV shows, so it should come as no surprise that she was on the radar for Sex and the City when it first went into production.

In an interview with Howard Stern, Bernhard revealed how she turned down the role of Miranda Hobbes because of the low paycheck and terrible script. "It has nothing to do with selling out; it just wasn't any good. Had it been a good script, had I thought it had legs, I would've done it. Even Cynthia Nixon admits it didn't catch on until the second or third season."

Bernhard also threw shade at Sarah Jessica Parker in the same conversation. "[I would've had] to play third or fourth fiddle to Sarah Jessica Parker and put up with her s**t. It would've been hideous to work with her."

Paul Shaffer

Paul Shaffer as George Costanza in Seinfeld

Rumor has it that had Jerry Seinfeld gotten his way, we would've had a different George Constanza in Seinfeld. The man he originally wanted before Jason Alexander was the multitalented Paul Shaffer. However, as it turns out, Shaffer had no real interest in the role.

According to Shaffer's memoirs, his receptionist received a message from Seinfeld, which said, "There's no audition. You've got the part. Just call us back!" Shaffer recalled his initial reaction, "I was kind of overwhelmed and I said, 'Jerry Seinfeld. What kind of show could he possibly get?'" He never returned Seinfeld's call.

Years later, Seinfeld shot down the rumor, saying, "Wrong. I don't know how that got started. Not true." It would be nice if we knew who's telling the truth here.

Whitney Houston

Whitney Houston as Sondra Huxtable in The Cosby Show

When you think of the late Whitney Houston, you remember her for the legacy she left behind in music. She was destined for greatness, and it's sad that her personal demons caught up with her as she passed away at the age of 48.

Her career could've turned out much differently had she accepted the offer of playing Sondra Huxtable in The Cosby Show, which eventually went to Sabrina Le Beauf.

According to an interview with director Jay Sandrich, Houston wanted to focus on her singing career. "So we gather in this room. And this girl who we brought from New York said, 'I can't sign this contract.' And I said 'Why?' She said, 'Well, I want to be a singer. I can't be in every show. I have to be able to tour.'"

Bella Thorne

Bella Thorne as Emma Duval in Scream

When the Scream TV series was announced, many fans were hesitant about it. First off, it would be aired on MTV. Secondly, what more stories could be told? Finally, who'd star in it?

Upcoming star Bella Thorne was originally approached to play Emma Duvall, the lead at the center of Lakewood's high school murders, but she declined. Thorne explained that it didn't work out because she was unwilling to relocate and be away from home.

In later interviews, though, Thorne said that she actually turned down the role because she was more interested in playing Nina, who died in the first episode, since it seemed like an iconic part – much like Drew Barrymore's character in the first Scream film. Or maybe the real truth is that Thorne just wanted more free time for Snapchat.

Connie Britton

Connie Britton as Olivia Pope in Scandal

Now, this is one role that we're glad went to the right person. When Scandal was picked up, Connie Britton was pitched by the network as the perfect person to portray Olivia Pope, and that's when the series creator, Shonda Rhimes, stepped in.

Speaking to the Hollywood Reporter, Rhimes said, "Nothing felt more important than the sense of outsiderness. I didn't know that there hadn't been a drama series with a leading black woman for 37 years. When the show got picked up [to pilot], I got a phone call from somebody who said, 'This would be the perfect show for Connie Britton.' I said, 'It would be, except Olivia Pope is black.'"

Considering the success of the show and Kerry Washington's performance, it's a godsend that Rhimes fought for this one.

Rachel Dratch

Rachel Dratch as Jenna Maroney in 30 Rock

When 30 Rock's pilot was shot, Rachel Dratch portrayed Jenna DeCarlo, Liz Lemon's (Tina Fey) best friend. Afterwards, the role was recast with a new pilot, and Jane Krakowski landed the part as Jenna Maroney.

Dratch spoke to the New York Post about the recasting. "When I was let go, I didn't think it was a big deal. The direction of the character had changed and pilots are recast all the time. I thought it would be a non-story, but suddenly it blew up." Dratch did go on to play multiple roles on 30 Rock and has said there are no hard feelings.

The less politically correct answer is that the network wanted a prettier actress in the role and thus cast Krakowski instead of Dratch.

Michael Keaton

Michael Keaton as Jack Shephard in Lost

To this day, Lost is still one of the most popular TV shows ever made, hence its main character, Jack Shephard (played by Matthew Fox), remaining a talking point for fans of the series. However, Fox wasn't creator, J.J. Abram's, number one pick for the part. That honor belonged to Michael Keaton.

Explaining the situation to Access Hollywood, Keaton said Abrams originally told him the character would die in the first episode."I said, 'I'll seriously consider it, send me the script,' [but Abrams] said, 'No, we're keeping the guy alive,' and I said, 'Oh, ok, well I can't do that.' An hour show every week... I've got stuff to do, I've got a life to lead. When would I fish?"

Well, we hope the former Batman actor still has enough time to go fishing.

Tamzin Merchant

Tamzin Merchant as Daenerys Targaryen in Game of Thrones

While it's impossible to imagine anyone else except Emilia Clarke as our Khaleesi, Daenerys Targaryen, there was almost another English actress in the role. In fact, Tamzin Merchant even filmed the pilot as Daenerys.

As the story goes, the original pilot was received so poorly by the people in charge that it meant the team had to go back to the drawing board. Sadly, this resulted in some of the actors being recast – Merchant included. Casting director Nina Gold told Variety, "It's terrible to disappoint. It's difficult to let down. That's hard. It's tough, but you've got to get it right, ultimately."

Despite being recast, George R.R. Martin has praised Merchant's performance. Maybe one day we'll get to see this mysterious pilot and Merchant's portrayal of Daenerys.

John Posey

John Posey as Danny Tanner in Full House

While you might think the TV industry is where dreams become a reality, it can easily become a nightmare. Just ask John Posey, who packed up his life in Atlanta and moved to Los Angeles to become Danny Tanner in the sitcom Full House.

"From what I was told, they were looking all over the country for people and couldn't find a guy, although I later found out that Bob Saget and Paul Reiser were the two guys they were after first, and they were both unavailable," Posey told Yahoo. Nonetheless, he went on to film the pilot for the show.

With his car full of his belongings and on the way to LA, Posey received a call from his agent. "[He said,] 'I don't know what's going on, but for some reason they're testing Bob Saget.'" The rest is history.

Ed O'Neill

Ed O'Neill as Al Swearengen in Deadwood

After starring as Al Bundy in Married… with Children for a decade, Ed O'Neill struggled to shake off the typecasting and branch out. So, when Deadwood writer David Milch approached him and said he'd crafted the part of Al Swearengen specifically for him, O'Neill thought the tide had turned in his favor.

Reportedly, Milch said, "You're going to be my Swearengen. It's done. You're gonna be f**king great." The only problem was, Milch had failed to tell any of this to the network.

Ultimately, HBO decided against casting O'Neill because of the fear that viewers wouldn't be able to separate the actor from his Al Bundy role. The part ended up going to English actor Ian McShane, who won a Golden Globe for his performance as Swearengen.

Scott Glenn

Scott Glenn as Clay Morrow in Sons of Anarchy

When Sons of Anarchy shot its pilot episode, Scott Glenn was cast as Clay Morrow. Not long afterwards, though, Glenn was replaced by Ron Perlman.

Speaking to The A.V. Club, Glenn confirmed what happened, "Yeah, I did the pilot, and then they called me up – I remember my agent called me up and said, 'Are you sitting down?' I said, 'Yeah.' 'The network is going to go ahead with the series, but not with you playing that part.'"

"So essentially, 'You're fired,' but, 'We liked the series, but we don’t want you for whatever reason.' And I have my own ideas about why that was, but what is it they say? When one door closes, another one opens? It was ultimately probably one of the better things that could've happened to me," he said.

Lily Allen

Lily Allen as Yara Greyjoy in Game of Thrones

In a Reddit AMA, Lily Allen claimed she was offered the role of Yara Greyjoy in Game of Thrones. It would've been a case of art imitating life, as Lily's brother, Alfie, plays the part of Theon on the show.

However, Lily said the sibling intimacy part freaked her out (obviously, she doesn't watch Game of Thrones on a regular basis). "They asked me if I'd be interested in playing Theon's sister. I felt uncomfortable because I would have had to go on a horse and he would have touched me. Once they told me what was entailed, I said no thanks."

After Lily's claims, though, her brother came out and said her story wasn't true and refused to elaborate. So, who's the telling the truth here?

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Did we miss out on any other actors who lost out on big TV roles for shocking reasons? Let us know in the comments section!