The Transplant - Season 2,Episode 9

Courage finds a bone in the backyard, which turns out to be the bone of the extinct kangaroo monster, as Courage's computer says (apparently, the scientists weren't very creative in the name). A whole skeleton is found, and Eustace sells bones to scientists. When Courage comes, Eustace accidentally falls off the roof, and their doctor says a bone transplant is needed. Courage decides to use the kangaroo monster bone to transplant into Eustace. The doctor puts the bone into Eustace. That night, Eustace turns into a kangaroo monster who takes Muriel and rampages the whole world!! The computer says the only thing that can defeat a kangaroo monster is another one. Courage goes to the doctor again who transplants another kangaroo monster bone (actually, a piece of the original that chipped off during Eustace's operation) into Courage. Eustace goes into France where he finds Courage has turned into a kangaroo monster as well! When Eustace goes on the Eiffel Tower, Courage throws crescent rolls that make Eustace fat and he falls off into a river. Courage rescues Muriel. In the end, the doctor removes Courage's bone, Courage is back to a dog and living with Muriel, and Eustace wins an award from France.