Ernie Hudson stated that playing the character "Captain Munroe Kelly" is his personal favorite from his career.
The "diamonds" used for the scenes during the climax of the movie were actually Herkimer Diamonds borrowed from the Herkimer Diamond Mines of Middleville, New York. They are doubly-terminated (two-ended) quartz crystals that are found in only two places in the world. They were the only gems that would look enough like diamonds and be that large. As a kind of tribute, Tim Curry's character's first name is "Herkermer" (his character does not appear in the Michael Crichton novel upon which the movie was based).
Contrary to popular belief, the lava effects were not CGI; they were created in miniature using a methylcellulose mixture and composited into the final shots.
Executive producer and director Frank Marshall originally intended to use the computer work pioneered on Jurassic Park: O Parque dos Dinossauros (1993) for the gorillas, but opted for models, as the computers weren't capable of reproducing hair.
The hippopotamus that attacks the team in the movie was a 2.5-ton animatronic puppet, controlled by off-camera puppeteers. A one-handed telemetry device controlled the head and neck while other puppeteers operated the animal's ear, nose, and eye movements. Its body was made from fiberglass, and silicone used for the skin.