Joseph Mazzello as Tim Murphy
Timothy "Tim" Murphy is Lex Murphy's brother and John Hammond's grandson. He is described as a bespectacled boy of about eleven who has an interest in dinosaurs and computers.
His quick thinking and encyclopedic knowledge of dinosaurs aid the group several times, and Tim is instrumental in discovering that dinosaurs have escaped the island, as well as regaining the means to warn the mainland in time.
Later, Tim's ingenuity and technical knowledge allow him to navigate the Park's computer systems and reactivate the physical security systems before the Velociraptors gain access to the visitor's lodge.
His expertise regarding dinosaurs rivals Dr. Grant's, and is clearly superior to that of Dr. Henry Wu, the scientist who created the dinosaurs. Already familiar with his work before they meet, Tim almost immediately strikes up a friendship with Dr. Grant.
According to Grant, "it's hard not to like someone so interested in dinosaurs". Tim's father doesn't share his interest in paleontology, so the dinosaur-loving Grant forms an instant bond with Tim during their time in the park.
In Spielberg's film, Tim and Lex's ages were swapped so that Lex was the older sibling and some aspects of his personality and story responsibilities were given to Lex.
For example, he is still the child interested in dinosaurs, however all of his computer knowledge was given to Lex. This was done so that Spielberg could work specifically with actor Joseph Mazzello, who was younger than Ariana Richards and to make Lex into a stronger character.
Bob Peck as Robert Muldoon
Robert Muldoon is Jurassic Park's game warden. Described as a burly man about fifty years of age with deep blue eyes and a steel gray mustache, Muldoon is a former wildlife hunter who worked with Hammond on one of his previous parks in Kenya.
He has experience working with dangerous predators and thus unlike most other characters, his attitude to the dinosaurs is realistic and unromantic. He also recommended that the park be equipped with more military grade weapons for use in emergencies, but was overruled.
Muldoon spends most of the novel riding around the park, drinking whiskey (at one point Hammond describes him as a drunk) and attempting to restore order. He is later attacked by a pack of Velociraptors, but survives by wedging himself into a pipe. He manages to kill a few of them, and eventually escapes the island with the other survivors.
In the film, his character is much more serious. During an attempt to restore power, Muldoon uses his fedora to set a trap for a Velociraptor which instead outsmarts and ambushes him. Because his death was never shown on screen, rumors that the character would return in future films, albeit scarred, persisted until Bob Peck's death in 1999.
Muldoon delivers one of the signature lines in the series: once realizing that the raptors have drawn him into a trap, he remarks casually, "Clever girl," the instant before he is attacked. In a deleted scene from the second movie, Muldoon's family received $12.6 million in his death settlement.
Martin Ferrero as Donald Gennaro
Donald Gennaro is the attorney sent on behalf of Jurassic Park's investors to investigate the safety of the park after several reports of missing or dead workers. He is described as a short, muscular man and represents an "everyman" personality among the characters.
When problems begin to occur, he consistently handles them appropriately, accompanying Robert Muldoon on a mission to subdue the Tyrannosaurus and successfully restoring power, despite being ambushed by a Velociraptor.
Gennaro then helps Grant in his attempt to wipe out the remaining velociraptors and their eggs with nerve gas. Though he survives the events on the island, he dies of dysentery sometime after.
For his film, Spielberg condensed the characters Ed Regis and Donald Gennaro and some of the negative aspects of Hammond into the same character. The result is a character who is cowardly, greedy, and often worried.
When the other scientists criticize Hammond's park for various reasons, Gennaro is the only one left who supports the concept. Despite this, he is described as a "blood-sucking lawyer" by Hammond himself.
In a deleted scene from The Lost World: Jurassic Park, it is stated that Donald Gennaro's family received $36.5 million from InGen in a settlement regarding his death.
Wayne Knight as Dennis Nedry
Dennis Nedry is one of the novel's human antagonists. He is described as an obese, messy computer scientist. Nedry works for Hammond as the system's programmer and is in charge of networking Jurassic Park's computers.
Though he was not given any details about InGen's operation, Nedry was expected to fix numerous bugs and issues without knowing the ultimate goal. He feels left out of the loop and doesn't feel like he is respected or paid enough for the very essential job he does.
This leads him to make a deal with Dodgson of Biosyn to steal several dinosaur embryos for $1.5 million. In order to do this, he shuts down the park's security systems, including several electric fences surrounding select dinosaur paddocks.
He intended to steal embryos from a secure lab, drive them through the park to a waiting agent at the dock, and return to his post before being noticed. Though it was only meant to be temporary, he crashes his Jeep and is subsequently blinded and killed by a Dilophosaurus.
In the novel, his body is later found by Muldoon and Gennaro; Muldoon reflects that Nedry's death was justice for his actions. Though Nedry's pride in his knowledge of complex computer systems made him feel more important than the other workers, Lex (film) / Tim (novel) is later able to easily navigate the system in order to restore power to the visitor's center.
In the sequel, Malcolm does not include him as one of the people whose deaths can be attributed to the park. This implies that his death is unknown to most of the characters who presumably believed he escaped the island. Nedry's role in the film is generally the same as that of the novel.
Samuel L. Jackson as Ray Arnold
John Raymond "Ray" Arnold is Jurassic Park's chief engineer, running the main control center from the visitor center. He is described as a thin, chain-smoking man, and a chronic worrier.
A gifted systems engineer, Arnold had designed weapons for the U.S. military and later worked at several different theme parks and zoos before joining the Jurassic Park team.
He was a grudgingly optimistic man, who maintained total faith in the computer systems and continued to believe that despite the setbacks, things would work out in the end. When Dennis Nedry locks them out of the system, Arnold, after much persuasion by Donald Gennaro, shuts off all power to the park and resets the computer-control systems.
In Spielberg's 1993 film, Arnold is occasionally referred to as "Ray", although his first name is John. This was done to distinguish him from John Hammond. This Arnold has a smaller role than in the novel but retains the same personality and outlook.
Arnold's death is not shown on camera, but is confirmed when his severed arm falls onto Ellie Sattler's shoulder in the power shed. In a deleted scene from the second movie, Arnold's family is said to have received a $23 million settlement from InGen in a lawsuit regarding his death.
Grant sighs and stands up. He and Ellie walk toward the source of the voice. As they walk, we get our first look at the badlands. Exposed outcroppings of crumbling limestone stretch for miles in every direction, not a tree in sight. In the dig itself, the ground is checkered with excavations everywhere.
There's a base camp with five or six tents, a flatbed truck, and a mobile home. There are a dozen volunteers of all ages at work in various places around the dig. A volunteer throws a switch on a machine that looks a bit like a floor buffer. The whole thing hops up into the air as it drives a soft lead pellet into the earth with a tremendous force.
There is a dull thud, the earth seems to vibrate. Grant and Ellie arrive to where several volunteers are clustered around a computer terminal that's set up on a table in a small tent, its flaps lashed open.
Volunteer #1: This new program's incredible. A few more years development and we won't even have to dig anymore.
Grant: Where's the fun in that?
The screen suddenly comes alive, contour lines tracing across it in waves, detailing a dinosaur skeleton, possibly a Velociraptor. Alan points to part of the skeleton, but when his finger touches the computer screen, the image changes. He pulls his hand back, as if it shocked him.
Grant: I hate computers.
Ellie: The feeling's mutual.
The original image comes back. Grant continues, but doesn't get as close.
Grant: Look at the half-moon shaped bone in the wrist. No wonder these guys learned to fly.
The group laughs. Grant is surprised. He explains that dinosaurs have more in common with present-day birds than reptiles. The pubic bone turned backward and the vertebrae hollow, just like a bird.
A kid steps forward and looks at the computer skeleton critically.
Volunteer Boy: That doesn't look very scary. More like a six-foot turkey.
Everyone sort of draws in their breath and steps aside, revealing the kid, standing alone.
Grant turns to the kid and stares at him like he just came from another planet. Grant strolls over to the kid.
Grant: A turkey, huh? OK, try to imagine yourself in the Cretaceous Period. You get your first look at this "six foot turkey" as you enter a clearing.
Grant: He moves like a bird, lightly, bobbing his head. And you keep still because you think that maybe his visual acuity is based on movement like T-Rex - he'll lose you if you don't move. But no, not Velociraptor.
Grant: You stare at him, and he just stares right back. And that's when the attack comes. Not from the front, but from the side, [makes 'whoshing' sound] from the other two raptors you didn't even know were there. Velociraptor's a pack hunter, you see, he uses coordinated attack patterns, and he's out in force today. And he slashes at you with this.
He takes a claw from his pocket and holds it as the front of the raptor's three-toed foot.
Grant: A six-inch retractable claw, like a razor, on the the middle toe. He doesn't bother to bite your jugular like a lion, say... no no. He slashes at you here, or here...
He lightly 'slashes' across the kid's body with the raptor claw.
Ellie: Oh, Alan...
Grant: Or maybe across the belly, spilling your intestines. The point is, you are alive when they start to eat you. So you know, try to show a little respect.
Volunteer Boy [mortified]: OK.
And with that Alan walks back across the camp, returning to his skeleton. Ellie hurries to catch up with him.
Ellie: Hey, Alan. If you wanted to scare the kid you could have pulled a gun on him.
Grant: Kids! You want to have one of those?
Ellie: I don't want that kid, but a breed of child Dr. Grant could be intriguing. I mean, what's so wrong with kids?
Grant: Oh, Ellie, look, they're noisy, they're messy, they're expensive.
Ellie: Cheap... cheap...
Grant: They smell.
Ellie: They do not smell.
Grant: Some of them smell.
Ellie: Oh, give me a break!
Grant: Babies smell!
A strange wind seems to be whipping up. Grant and Ellie look around, confused. The wind is getting stronger, blowing dirt and sand everywhere, filling in everything they've dug out, blowing the protective canvasses off.
Now there's a more familiar roar, and they look up and see it - - a helicopter descending on the camp. Down at the base camp, the helicopter has landed. Grant comes down like Moses steaming. Grant gestures wildly at him to turn the chopper off. The pilot points timidly to a mobile home across the camp. Grant runs to the trailer.