In the spring of 2001, DreamWorks released its computer-animated movie, Shrek. The movie revolves around a terrifying-looking ogre who is on the verge of losing his beloved swamp after Lord Farquaad sends unwanted mythical creatures out of his city and to Shrek's land. Shrek then goes on to make a deal with Lord Farquaad to get his peaceful swamp back, making friends along the way.

RELATED: Everything We Know About Shrek 5 So Far

The animation and premise of Shrek were a hit, making it one of the most successful animated comedies to date. The original film just ed its 20th anniversary and a fifth Shrek movie is set to release in 2022With the ing of the 20th anniversary, there are plenty of behind-the-scenes tidbits that fans don't know about this beloved movie.

Shrek Is Based On A Children's Book

A split image of Shrek and Donkey next to the Shrek book

Before Shrek became one of the best movies of the 2000s, it was actually based on the children's book Shrek! by William Steig.

The book was released in 1990 and according to its Amazon description, was "about an ordinary ogre who leaves his swampy childhood home to go out and see the world." The movie is obviously altered slightly from the book but Shrek's appearance and ending with Princess Fiona are the same.

Some Of The Actors Never Met Each Other While Recording

A split image of Mike Meyers and Cameron Diaz recording Shrek

With great characters and funny quotes, fans can assume that filming Shrek was a fun time. With comedians and actors like Mike Meyers, Cameron Diaz, and Eddie Murphy voicing Shrek's characters, the movie had an iconic line-up of funny talent.

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But according to Parade, the actors didn't record together. "They all read their parts separately," the source wrote. This meant that all of the banter between Shrek, Donkey, and Fiona were done on separate days, so the cast likely didn't mingle all that much.

Children Weren't Fond Of Princess Fiona In The Test Screening

Princess Fiona giving her hankerchief to Shrek

Being a DreamWorks movie, Fiona differs from the typical Disney princess. At the start of animating Shrek, animators found out that audiences didn't resonate with the original Fiona they had designed.

According to NPR, animators "re-imagined Princess Fiona as a slightly more cartoony-looking love interest" after audiences felt she was too human-like compared to Shrek. They then shifted her as more cartoonish and it worked.

Someone Else Was Supposed To Voice Shrek

Shrek scaring others in the forest on Shrek

One thing that some fans may not know about Shrek is that legendary comedian and SNL star, Chris Farley, was set to voice Shrek. He even recorded most of Shrek's dialogue for the film. In 1997, however, the comedian died unexpectedly, leaving DreamWorks at a loss for how to move forward with the character.

According to Insider, creators asked Farley's friend and fellow comedian, Mike Meyers, to take his role and re-do the vocals for Shrek. Meyers signed on and the rest was history.

Shrek Took A Long Time To Complete

Shrek leaving the outhouse

Shrek is a 90-minute film that took four and a half years to complete, according to  funny quotes and witty comebacks, the most difficult part about Shrek was animating every scene.

The characters, multiple locations, and action scenes had to be realistic enough for computer and clay animation, taking years to complete. The same can be said for the second, third, and fourth movies.

The Original Princess Fiona Was Fired

Princess Fiona in her dungeon on Shrek

Princess Fiona is one of Cameron Diaz's best roles. She's fierce, confident, and independent. However, Cameron wasn't the film's first actress for Fiona. What Culture noted that comedian Janeane Garofalo signed on for the role of Fiona, but without reasoning, was fired.

RELATED: 10 Best Cameron Diaz Movies, According To IMDb

They brought Diaz in once Mike Meyer's signed on, so it's possible that DreamWorks redirected the characters' personalities after Meyers was hired — leading to the firing of Garofalo.

A Few Days Of Voice Work, Years Of Animation

A promo for Shrek with Shrek, Fiona, Donkey, and Lord Farquaad

Now that fans know that the voice actors didn't record together, it turns out that recording didn't take very long either. During an interview with Ellen Degeneres, Cameron Diaz said that the voice work only took a couple of days compared to the work of the animators.

"I went in and I did one day, probably half a day, probably four or five hours. I did half the film — the voice of the film. And then a year later, I went back and did another five hours and did the second half of the film."

Shrek Has His Own Star On The Walk Of Fame

Shrek's star on the Hollywood Walk of Fame.

Due to Shrek's love of pop-culture references, the character would be honored to know that those in Hollywood felt he and his film deserved its own star on the Hollywood Walk of Fame.

In 2010, Shrek was awarded his own star, making him the 2,408th star on the Walk of Fame. To celebrate Shrek's big win, his voice actor, Mike Meyers, was there (along with a mascot-version of Shrek) to accept and celebrate the honor.

A Monumental Credit In Animation

Donkey and dragon in the forest of Shrek

Shrek is one of the top-performing animated comedies. With five movies, specials, a musical, and multiple games — it's an incredibly successful franchise. In fact, in 2001, Fox News noted that the Oscars added a new category to its awards, Best Animated Feature, and Shrek won.

Taking away the inaugural award at the Oscars makes the film a part of history. Shrek's sequel (Shrek 2) also won Best Animated Feature in 2004.

Alan Rickman Chose Snape Over Lord Farquaad

Lord Farquaad in bed drinking a martini

Before Shrek was released, famed actor, Alan Rickman, was known for his time in Die Hard and various TV shows and plays. While in production, Alan Rickman was offered the role of Lord Farquaad.

However, Farquaad went on to be the face of many memes and was a great antagonist in the franchise.