Hold onto your butts, Jurassic Park is 30 years old. 

Directed by the legendary Steven Spielberg and adapted from Michael Crichton's book, Jurassic Park premiered in 1993 and became a pop culture phenomenon that—unlike the dinosaurs—stood the test of time and changed the technology used in movies forever.

Like life, Jurassic Park finds a way: Five sequels and more than $6 billion at the box office later, the franchise has become one of the world's most successful and enduring film series. Sam Neill, Laura Dern and Jeff Goldblum introduced audiences to the magical—and sometimes terrifying—world of dinosaur clones in the original trilogy, while Chris Pratt and Bryce Dallas Howard led the second installment of films. But the two casts came together for 2022's Jurassic World: Dominion, the sixth movie in the franchise. Talk about a colussos occasion.

But did you know that Harrison Ford could have starred in the original movie? Or that two Jurassic Park co-stars were once engaged?

Tear into these 20 secrets you might not know about the Jurassic Park franchise...

1. Steven Spielberg and author Michael Crichton were in the early stages of developing a movie based on Crichton's time as an emergency room physician when he told the E.T. director about his book Jurassic Park. Spielberg's interest was immediately piqued and the other film was scrapped—but years later, the filmmaker helped to develop the story into the iconic medical drama E.R., which ran for 15 years on NBC. 

2. Universal bought the film rights to Chrichton's novel for $2 million before it was released in 1990. Titanic director James Cameron revealed in a 2021 conversation with Spielberg that he was hours away from making a bid before discovering he had already lost out to Jaws filmmaker.

"It was the very best thing that could have happened because I would have made it like Aliens," Cameron said. "I would have made an R-rated, scare-the-crap-out-of-you movie and you made it just scary enough."

3. During a 30th-anniversary screening of Indiana Jones and the Raiders of the Lost Ark in 2011, Spielberg let slip that Harrison Ford passed on the role of Dr. Alan Grant.

4. Other actors who were up for the part included William Hurt and Richard Dreyfuss, with New Zealander Sam Neill ultimately being cast as the archaeologist.

5. Laura Dern beat out Gwyneth Paltrow, Helen Hunt, Sandra Bullock and Robin Wright to play Dr. Ellie Sattler. Dern later revealed that it was her Wild at Heart co-star Nicholas Cage who convinced her to do the movie. 

"I said to him, 'Nic, they want to put me on the phone with Steven Spielberg, but they want to talk to me about a dinosaur movie,'" she told Entertainment Weekly in 2013. "And he was like, 'You are doing a dinosaur movie! No one can ever say no to a dinosaur movie!...Are you kidding? It's a dream of my life to do a movie with dinosaurs!' So he was such an ­influence on me."

6. While Jeff Goldblum was the first choice for Dr. Ian Malcolm, Jim Carrey had a "terrific" audition, according to casting director Janet Hirshenson, who told EW, "I think pretty quickly we all loved the idea of Jeff."

7. But Goldblum revealed that his character was almost cut from the movie. 

"I'd quickly read the book in preparation and Steven said, 'Since we scheduled this meeting, there's an idea afoot to combine the two characters, to absorb your character into the Sam Neill character,'" the actor explained. "I said, 'Well, geez. I hope you don't do that.' I might have even advocated on the spot, and I came back and lo and behold I had a little part in it."

8. Christina Ricci was in consideration for Lex Murphy, but Ariana Richards won the part for an unusual reason. "I was called into a casting office, and they just wanted me to scream," Richardson shared. "I heard later on that Steven had watched a few girls on tape that day, and I was the only one who ended up waking his sleeping wife off the couch and she came running through the hallway to see if the kids were all right."

9. After initially auditioning for Spielberg for 1991's Hook and being told he was "too young," Joseph Mazzello was cast as Tim after the director vowed to get him in another movie. "Not only a nice promise to get, but to have it be one of the biggest box-office smashes of all time?" Mazzello said. "That's a pretty good trade."

10. Goldblum and Dern began dating after production ended and got engaged in 1995. However, the co-stars broke up two years later.

"I was struck, I'd been a big fan of hers," Goldblum told The Chicago Tribune in 1993. "I think she's an amazing actress, and a spectacular person. I was struck from the beginning. But after the movie we realized we liked each other."

11. To achieve the Tyrannosaurus' infamous roar, the sound design team mixed together a dog, penguin, tiger's snarl, alligators gurgle, and a baby elephant's squeal, according to The Making of Jurassic Park: An Adventure 65 Million Years in the Making.

12. During filming, however, Spielberg would provide T-Rex's roars for the cast. "Steven was holding a bullhorn and roaring in a not very convincing way," Neill admitted to EW. "It's difficult enough acting to a tennis ball, but it's even harder when you're trying not to laugh."

13. On the last day of production, Hurricane Iniki—the most powerful storm on record to hit Hawaii—touched down. The cast and crew being emergency airlifted to Los Angeles, where they finished filming.

14. To get everyone safely off the island, producer Kathleen Kennedy "jogged to the airport" and then hitchhiked her way to Honolulu," where she eventually bumped into someone she recognized, Spielberg told EW.

"It was the young man that flew the biplane in Raiders of the Lost Ark," the director shared. "He was the pilot that was in our movie and he just happened to be a pilot of a four-engine 707, a cargo plane and he was between flights. So Kathy arranged with him to send a large plane to the island the next day to take the cast and crew out. It's once again something else that seems to only happen in the movies. And when things like that happen in the movies, the audience rejects that!"

15. After two sequels were released in 1997 and 2001, Jurassic IV was in development for years, beginning in 2001 and went through various changes before it was postponed in 2008. Several reportedly in consideration to appear in the film included Keira Knightley and Jeremy Piven.

16. Before landing the starring role in 2015's Jurassic World, Chris Pratt predicted his casting years earlier in a behind-the-scenes video he filmed for his TV series Parks & Recreation.

"As I was doing it my phone rang and I pretended that I had gotten a text from Steven Spielberg that I was going to be in Jurassic Park 4," Pratt told IMDb. "The bit was so funny because I was like, 'There is no way Steven Spielberg is going to cast you in Jurassic Park 4. That's funny!' And then it turned out that it happened which is wild. I manifested it."

17. Before Pratt was cast, Josh Brolin also auditioned for Owen Grady, with director Colin Trevorrow telling film critic Drew Turney in 2015 that, "I thought he would have been a great Owen and I still do....He was one of the people being considered. People hear that and it turns into a giant story. In the end, no offer or decision was made until we made an offer to Chris Pratt and he accepted it."

18. Bryce Dallas Howard revealed in a 2014 interview on The Tonight Show Starring Jimmy Fallon that her son Theodore Gabel had a small cameo as the little boy hugging the long neck in the petting zoo in Jurassic World. 

19. After working with Jurassic World: Fallen World director J.A. Bayona on The Impossible, Tom Holland was in talks to appear in the 2018 movie before he landed the role of Spider-Man. 

20. While Goldblum briefly appeared in Jurassic World: Fallen World, Jurassic World: Dominion, marks the first time he'll be sharing the screen with Dern and Neill screen since 1993. 

Jurassic Park is streaming on Peacock.