After Mickey's adventure on Treasure Island, Professors Ecks and Doublex read about his heroics and decided he was perfect for their evil experiments. They send Mickey a letter telling him to come to their castle, Blaggard Mansion, that night. Horace Horsecollar, suspicious of the invite, went with Mickey. After they arrived at the mansion, Horace was captured by Ecks and Doublex, who tested out their mind-control ray on him. They then sent the brainwashed Horace to capture Mickey, but they turned off the ray before the job was done, and he was able to tell Mickey all about it. Mickey was able to make a helmet out of a pewter pot, which protected his own brain from the effects of the ray. When Ecks and Doublex saw that their ray did not affect Mickey, they sought help from their leader, Professor Triplex, who assumed that the machine wasn't fully perfected and they needed to further experiment on Horace. However, before the three scientists could do that, Mickey took control of the mind-control ray and brainwashed the trio into being good scientists who would only work for the good of humanity.
Gottfredson never featured the three professors in another story after Blaggard Castle, but they were memorable enough to return to being mad scientists in stories under other authors in the 1970s.
In 1990, Ecks and Doublex appeared in a few issues of Mickey Mouse Adventures, now as a two-headed creature called Dr. Doublecross after an incident with a cloning ray.
In the August and September 1993 issues of Disney Adventures magazine, a comic story titled The Perils of Mickey: Return to Blaggard Castle was published as a sequel to the original story. Mickey, Minnie, and Horace Horsecollar are invited to the reconstructed Blaggard Castle, which has been turned into a museum chronicling Mickey's defeat of the mad Professors. However, it is revealed to be a trap set by the Phantom Blot designed to defeat Mickey once and for all. Ecks, Doublex, and Triplex themselves do not appear, though the Blot spends most of the story disguised as Triplex and cardboard cutouts of Ecks and Doublex appear. According to the Phantom Blot, the hypno-ray, while hypnotizing them into being good, did not keep them sane, which resulted in them going to jail, where they told the Blot about their encounter with Mickey.
Floyd Norman wrote a three-week Mickey Mouse comic strip storyline, which ran from December 26, 1994, to January 14, 1995, that provided another explanation for Ecks and Doublex's return to crime. In the story, titled "Reform and Void", Ecks and Doublex visit Mickey and provide him with many of their inventions to help him out. But while on a picnic, Morty and Ferdie splash Ecks with a water balloon, and then he does the same to Doublex. As a result of the two being splashed by water, the hypnosis on the professors is undone and they revert to their evil ways.