Unlike other badniks, Tails was not completely encased within a robot and did not serve as an organic battery. Instead, he was wearing a robotic exoskeleton over half of his body.
Tails had been brainwashed into hating Sonic, even going so far as to attack his former friend and accuse him of running off to play the big hero while Tails was left behind in the Green Hill Zone (despite him loving that Zone). When Tails saw Robotnik nearly crush Sonic with his Flying Egg, Tails remembered that Sonic was his friend and managed to resist and break free of Robotnik's control. He attacked Robotnik, shattering the Robofox exoskeleton and forcing Robotnik to flee.
Robotnik later recovered the original Robofox armour and gave it to the Arachbot, once again intending to trap Tails inside it. Arachbot briefly debated what Tails would be called once turned into a badnik in this way, contemplating the names "Foxy-bot" and "Tails-nik". However, Sonic was able to use the exoskeleton to defeat Arachbot: first, by tipping oil out of the suit, then using the suit's weapons system, a flamethrower, to set the oil alight. Arachbot was destroyed in the flames.
Sonic the Hedgehog Adventure Gamebooks
Tasnik, the badnik version of Tails from Sonic the Hedgehog Adventure Gamebook 4: The Zone Zapper, bears many similarities to Robofox. Robotnik developed a ray known as a Zone Zapper which turned everything it touched into a badnik or trap. Sonic evaded the beam, but Tails sprained his ankle and was transformed into the Tasnik. Sonic eventually freed Tails and returned him to normal.
- Tails' semi-mechanical form in Sonic Lost World may be a reference to this form, as they share a generally similar appearance and behavior. However, this Tails is openly hostile to Sonic until the exoskeleton is removed, whereas the Lost World equivalent is still himself due to the machine being reprogrammed.