Thanks to an asteroid and poor near-Earth object collision detection at the time, dinosaurs weren't around to show up in Jurassic Park. The film instead used practical effects and computer animation to bring the creatures to life, which is probably much safer than using actual dinosaurs anyways. But that's not without its own perils. Joseph Mazzello, who played Tim in the film, found this out the hard way when he was injured by a dinosaur on set, as he explained:
What Joseph Mazzello is describing is part of the memorable kitchen scene where one of the raptors chases Tim into the freezer, and he and Lex manage to lock it inside. This is just one of the many traumatic experiences Tim endures during the course of Jurassic Park, but it sounds like actor Joseph Mazzello suffered a real injury as well during this scene.
You can imagine how this could happen filming a scene like this, where he had to run and turn with a raptor on wheels close behind him. All it took was for him to look up and the raptor to go the wrong way. Boom, raptor claw to the head!
Thinking back to Jurassic Park, you might have thought that one of the parts where Tim is climbing, like the electric fence scene, would have had the greater potential for injury, but I guess this just shows that even artificial raptors are not to be trifled with.
Fortunately, the nine-year-old Joseph Mazzello had only suffered mild head trauma and was just a bit dazed from his run in with the metal claw. It sounds like it was quite the memorable experience too, considering, as Joseph Mazzello told Today that it happened on his birthday.
So in order to give the kid a break, Steven Spielberg made sure he was okay and had everyone sing him 'Happy Birthday.' That's got to be something, being that young, on a movie set with fake dinosaurs and having people sing to you. Sure, getting hit in the head couldn't have been fun, but spending your ninth birthday on the set of what would become an iconic film and having legendary director Steven Spielberg sing you 'Happy Birthday,' I'd say that's a net win.
With the new Jurassic World films, we often talk about the brief return of Jeff Goldblum's Ian Malcolm in Jurassic World: Fallen Kingdom and our hopes to see original characters like Laura Dern's Ellie Sattler or Sam Neill's Alan Grant show up in Jurassic World 3. That would be awesome, but it would also be great to see Joseph Mazzello's Tim and/or Ariana Richards' Lex appear in the new trilogy.