Rudy had followed Sid through the Plates of Woe, a rock formation consisting of massive rock plates, and had, in the pursuit, broken his way through the plates, leaving a vast field of rubble and broken rock behind. Rudy had discovered that a herd of mammals had entered the dinosaur world, led by Buck himself with that, Rudy began to track them down, first finding clues as to the whereabouts of Sid, a ground sloth and one of the mammals that was in the dinosaur world: Sid had been abducted by a Tyrannosaurus named Momma. Rudy since then held a grudge against Buck for taking his tooth: the dinosaur loathed Buck, who, in turn, saw Rudy as a challenge of the greatest kind, a worthy opponent.

Buck used the tooth as a weapon from there on and the encounter left Rudy to reoccur in Buck's dreams and thoughts continuously. Before Buck fell into the dinosaur's stomach, he managed to crawl his way out of Rudy's throat, holding onto his uvula, and launched himself from Rudy's mouth, knocking out one of his teeth. To escape the dinosaur, Buck climbed a tree that reached a massive height above the clouds of the dinosaur world, but Rudy managed to catch Buck and swallowed him. When Buck, a weasel, had fallen into the dinosaur world, Rudy emerged from the shadowy jungles and attacked Buck, with his claw blinding Buck's right eye. A massive apex predator, Rudy was feared by all creatures in the underground world where he lived, save for Buck, who relished the challenge of dueling the carnivorous dinosaur.

Ice age 1