Assistant to Dr. Alan Grant. Billy knew quite a bit about computers and technology, much to the dismay of the “mechanically impaired” Grant. Billy went along when Grant was hired by the Kirbys, but only because Grant didn’t want to be alone with total strangers. Along the way to Isla Sorna, Billy told Grant the story of how when he and some friends were hangliding in New Zealand, an updraft swept him against a cliff. He had been saved by the strap of his camera bag. Since then, it became his “lucky” strap. Once on the island, Billy foolishly decided to take two Velociraptor eggs from their nest, hoping to sell them to further fund his and Grant’s digs. Because of this, the group was soon relentlessly pursued by the eggs’ angry parents, who killed Udesky. When Grant learned what Billy had done, he was furious. But, when Eric Kirby was endangered by Pteranodons, Billy redeemed himself in Grant’s eyes by strapping on the Dino-Soar parachute they’d found and risking his life to save Eric. He fell into the water, and the Pteranodons pecked ceaselessly at him. The others thought he’d been killed, but he later turned up alive when the Navy and Marines came. He’d rescued Grant’s lost hat as well, which he returned to his grateful mentor. Billy Brennan was played by Alesandro Nivola.