12 things you probably didn't know about 'Jurassic Park'

"Jurassic Park" runs for 127 minutes.

Even fewer minutes were dedicated to CGI dinos.

During the first T. rex attack, the dinosaur breaks through the van's sunroof, terrifying both Tim (Joseph Mazello) and Lex (Ariana Richards).

It turns out the dino wasn't supposed to break the glass.

"I think the T. rex was only supposed to go down so far, and the Plexiglass was the only thing between the dinosaur and us. It came down too far one time, and it chipped the Plexiglas and broke a tooth." Mazzello told EW.

It is almost impossible to know what a dinosaur actually sounded like, so Spielberg and the crew drew inspiration from modern animals.

The velociraptor was a mixture of both dolphin and walrus. Meanwhile, the T. rex was a mixture of a lion and at times, a baby elephant.

And in case you were hoping to be scarred for life by a childhood classic, many of the sounds the dinosaurs made were actually the recorded noises of animals having sex.

Actual dinosaur sounds weren't added into the film until post-production. In order to give the actors authentic, fearful looks at the creatures, Spielberg would make the noises himself.

During the raptor pen scene, Spielberg made as many dinosaur sounds as possible through a bullhorn.

"Steven was holding a bullhorn and roaring in a not very convincing way. It’s difficult enough acting to a tennis ball, but it’s even harder when you’re trying not to laugh." Sam Neill told EW.

Spielberg was inspired to do this shot after listening to an Earth, Wind, and Fire song in his car, which caused the mirror to shake.

So Special Dinosaur Effects Supervisor Michael Lantieri had to find a way to recreate this onscreen.

"The mirror shaking was really very easy ... but the water was another story," Lantieri said in an interview from the "Jurassic Park" Blu-ray. "It was a very difficult thing to do. You couldn't do it. I had everybody working on it. And finally, messing around, with a guitar one night, I set a glass, I started playing notes on a guitar and got to a right frequency, a right note, and it did exactly what I wanted it to do."

To replicate that for the shot, they "fed a guitar string through the car, down to the ground, and then I had a guy lay under the car and pluck the guitar string," Lantieri said in another interview from an early "Jurassic Park" DVD.

"Jurassic Park" featured a groundbreaking mixture of practical and digital effects.

Upon looking at some of the first footage of a CGI T. rex, Dinosaur Supervisor Phil Tippett (who dealt with traditional stop motion animation) turned to Spielberg and said, "I think I'm extinct."

Spielberg ended up using Tippett's line in the movie.

After the three scientists witness living, breathing dinosaurs for the first time, Dr. Alan Grant (Sam Neill) says "I think we're out of the job." Ian Malcolm (Jeff Goldblum) responds, "Don't you mean extinct?"

Squint during this clip and you'll see Dennis Nedry (Wayne Knight) is watching "Jaws," Spielberg's other legendary monster movie.

Nedry is in the middle of watching the scene where Chief Brody (Roy Scheider) is shoveling chum in the water, and the shark pops out of the water for the first time.

Because most of the dinosaurs were added in during post-production, actors were typically screaming at nothing.

While the first T. rex scene used a mixture of animatronics and CGI, the finale required a dinosaur designed completely on a computer.

So the actors would know what they were screaming at, the crew put up what Spielberg called "barber polls," which were giant polls with a T. rex face attached to it. These helped give "lighting references" to the guys who created the computer generated T. rex.

"You set the camera up in the room and you shot as if there was a full-size animal in the room with the actors," Spielberg said in a behind-the-scenes feature.

According to Pajiba, Dern had some competition from Jodie Foster, Joan Cusack, Julia Roberts, Linda Hamilton, Sarah Jessica Parker, Sandra Bullock, Gwyneth Paltrow, and Helen Hunt.

Julianne Moore also auditioned for the role, and while she didn't make the cut, she remained on Spielberg's radar: Moore was cast as Sarah Harding in the 1997 sequel "The Lost World: Jurassic Park."

Apparently, Dern was Spielberg's first choice all along. However, it took some convincing from Nicolas Cage for her to accept the role.

Spielberg and Harrison Ford have had a successful run together. After all, thanks to them, the world got Indiana Jones. Yet, their successful working relationship was not enough to convince Ford to take the role of Dr. Alan Grant.

Sam Neill ended up playing Dr. Grant. According to EW, he took a call from Spielberg while on the way to Canada and two days later, the part was his.

The first appearance of the T. rex had such an impact on Spielberg that it inspired him to change the movie.

"I think the star in our movie is T. rex. The audience will hate me if the T. rex doesn't come back and make one more heroic appearance," Spielberg said in a making of documentary.

The original ending took place in the same rotunda but instead of a fight with the T. rex, one of the raptors gets stuck in a big T. rex skeleton and gets killed after it crashes to the ground.

See where the cast of the original film is 22 years later >