9+ Actors Who Were Suddenly Replaced While Filming Fan Favorite TV Shows

For Season 1 of Riverdale, the cocky, football-playing jock Reggie Mantle was played by actor Ross Butler.

However, the show hit a snag when Butler was cast in Netflix's hit, 13 Reasons Why.

The producers quietly swapped out Ross Butler for Charles Melton.

Reggie's role on the show has grown a lot since Ross Butler originated the role.

In fact, while Reggie was dating Veronica, Charles was dating Ronnie's actress, Camila Mendes!

For three seasons, Aunt Vivian was played by Janet Hubert in The Fresh Prince of Bel-Air.

While everything was fine with the Banks family on-screen, off-screen was a different matter entirely.

She alleged that, during salary negotiations for the rest of the cast, Smith refused to help his fellow castmates negotiate for higher wages.

The conflict between them eventually led to Hubert being fired.

She was replaced by Daphne Maxwell Reid. At least the show acknowledged the swap!

Remember Ross' ex-wife, Carol? She left him for another woman, Susan, but later found out she was pregnant with his child.

Yeah, there were actually two different Carols in Friends. Weird, right?

Anita Barone originated the role, and she wasn't satisfied with how small it was at the time.

Of course, Jane Sibbett stepped in, and Carol's role did end up being much bigger. Oops.

John Posey originally won the role of Danny Tanner in Full House and was still in the role when the show was ordered to series.

The producers went ahead and screen-tested their actual preferred choice of Bob Saget as Danny, anyway, and ultimately gave Posey's role to him. Ouch.

In a move that was probably better for her in the long-run, Jenna Fischer was recast after the pilot episode of Man With a Plan was shot.

Jenna and star Matt LeBlanc didn't have the right chemistry, so the producers fired her and replaced her with Liza Snyder.

When the pilot of Gilmore Girls began production, a very different woman took on the role of Sookie St James: Alex Borstein, who you probably know best as the voice of Lois in Family Guy.

Borstein got stuck on her show, Mad TV, and the role of Sookie was recast with Melissa McCarthy.

However, Borstein eventually made it to Stars Hollow — as a very quirky harpist.

Emilia Clarke is Daenerys Targaryen, and Daenerys Targaryen is Emilia Clarke. There’s no separating the two when it comes to the Mother of Dragons.

Originally, Tamzin Merchant was set to play Dany, and shot the original Game of Thrones pilot in the role.

She was recast during the pilot reshoot, and the rest is television history.

What happens when you need to find an actor who can quite literally fill the shoes of The Mountain?

Well, you try one, and then...you try another. And then, when things aren't working, you cast yet another.

Originally, the Mountain was played by Conan Stevens.

Ian Whyte took over the role afterward, and then Hafþór Júlíus Björnsson eventually got the role in season 4.

He stayed in it for the rest of the show.

When you picture the The Big Bang Theory, it's impossible not to think of Kaley Cuoco's Penny.

However, Kaley was not the originator of the role — in fact, at one point, Penny didn't exist at all.

Amanda Walsh was cast as Katie, Sheldon and Leonard's neighbor.

She was recast after coming across too mean, and was generally not the right fit for the role. So, in came Penny and Cuoco.

Her?

Alessandra Torresani might be familiar to you as Claire from The Big Bang Theory or Zoe from Caprica, but she played the role of sweet, yet forgettable Ann Veal on Arrested Development in its first season.

In a sort of fitting move for a character designed to be plain and forgettable, many people didn't notice the change when it happened.

The showrunners actually planned on consistently recasting Ann to play into the joke, but they ended up liking Mae Whitman enough to keep her.

In probably one of the most confusing cast switch-ups, Alicia Goranson, who had the role of the oldest Conner child for five seasons, went off to college, so they replaced her with Sarah Chalke.

But not entirely.

Poor Becky Conner switched between Goranson and Chalke multiple times over the remaining seasons.

The show made a joke out of it, having multiple characters acknowledge Becky's constantly changing appearance, and in the 2017 continuation, Chalke returned to play a woman who wants Becky to be her surrogate.

Twins Jaden and Ella Hiller played the adorable baby Lily Pritchett for the first two seasons of Modern Family, but according to their parents, they didn't enjoy the experience and didn't want to continue.

It worked out well for the show, though, who recast the twins with slightly older Aubrey Anderson-Emmons, who had the benefit of being able to walk, talk, and read lines.