Dr. Caballeron first appears in the episode Daring Don't during a scuffle between Daring Do and a group of stallions who work for him. When the thugs incapacitate Daring, Caballeron seizes a gold ring that the two sides were fighting over and smugly thanks Daring Do for finding the ring for him. He reveals to Daring that he's working with Ahuizotl and intends to sell the ring to him, make a fortune, and retire in splendor. What Ahuizotl intends to do with the ring is apparently of little consequence to him.
In the forest, Dr. Caballeron and his henchponies encounter a disguised Daring Do who offers a large bag of bits for the ring. With Ahuizotl not present, Caballeron is eager to sell. When Ahuizotl angrily storms onto the scene, Caballeron makes off with the bits and leaves the ring behind.
Rainbow Dash states in the episode Dr. Caballeron made his debut in the book series' fourth entry, Daring Do and the Razor of Dreams. He is stated to have wanted to partner up with Daring Do on her adventures, but Daring Do refused.
In Stranger Than Fan Fiction, Dr. Caballeron and his henchponies pursue Daring Do to a Daring Do Convention in Manehattan, and he expresses displeasure at not being more popular with Daring Do fans. In order to claim an artifact that Daring recently found, he abducts Rainbow Dash and Quibble Pants to bait her into the open.
After his attempt to find a rare treasure ends in failure, Caballeron and his henchponies are chased off by a ferocious Cipactli.
In Daring Done?, Dr. Caballeron attempts to ruin Daring Do's reputation in the southern village of Somnambula so that he can make off with the village's collection of glowpaz and frame Daring Do for the act. He and his henchponies briefly capture Rainbow Dash as bait to lure Daring Do into a trap, but Daring, Rainbow, and Pinkie Pie eventually thwart his plan, exposing his deception in the process.