Having been created as an insult to Tails, Tails Doll was sent into New Mobotropolis by Dr. Eggman, armed with a nanite disruptor that appeared to be a red gemstone. It was picked up by Cream the Rabbit during Titan Metal Sonic's assault on the city. Thinking it was just a doll that somebody had dropped in the panic, Cream decided to hold onto it until she could return the doll to its owner. (StH: #231, CSE)
Later, when Cream became a member of Team Freedom, her mother, Vanilla, held onto the doll for her during the team's inauguration. The doll then emitted a strange sphere of energy around itself in a large area, unbeknownst to anyone else, which seemed to make the Nanites inside of the area disappear. This caused a nearby building to begin falling over, but Rotor Walrus, the leader of Team Freedom, quickly, tactically, and successfully ordered the team to stop the impending danger before anyone in the crowd could get hurt. (StH: #236)
During Dr. Eggman's invasion of New Mobotropolis, when the Death Egg hit the city's shield, Eggman revealed that Tails Doll was supposed to infiltrate and taken care of the city's defenses, but had taken damage during entry. At that moment, Tails Doll reported in that it was moving into position and it lead to New Mobotropolis' shield generator in the power plant on its own. It used the nanite disruptor on its head to melt the shield generator, causing the shield to disappear and allowing Dr. Eggman to infiltrate New Mobotropolis successfully. (StH: #240)
Later when Mina and the Forget Me Knots attempted to hold a concert to inspire people to want NICOLE back, the Tails Doll sneaked away from Cream and secretly used the gem on its head to destabilize the stage, causing it to collapse, Mina and her band were saved by Team Freedom, Mina then used this event to convince the people that they need NICOLE to keep the city stable. Tails Doll later pulled a similar stunt at the dedication of the rebuilt Castle Acorn, but its true nature was realized by Cream, who informed Rotor. Setting a trap for the doll, Team Freedom intercepted it when it left Cream's house and went to the power station in an effort to destroy it again. Having repaired itself, Tails Doll utilized its disruptor to commandeer a number of nanites, which it used to transform into a monstrous-looking creature. It then announced its intentions to destroy New Mobotropolis by destroying the power plant and then flooding the city with radioactive waste from Robotropolis. Furthermore, in order to accomplish its goal, it set its sights on Team Freedom's annihilation. However, the combatants were subsequently hit by the effects of the second Genesis Wave. (StH: #241, #247)
Tails Doll, unlike the majority of Eggman's robots, has demonstrated limited mobility and little in the way of fighting power in its natural state. It's greatest weapon is the nanite disruptor on its head, which gives it a variety of abilities. According to NICOLE, it works by blocking nanite signals, erasing their programming, and even causing them to self-destruct. On one occasion, its powers allowed it to reduce the city's shield generator to a molten mass. It can also apparently take control of nanites, allowing Tails Doll to reshape them and change its form.
As its name suggests, Tails Doll resembles a patchwork doll version of Tails. Its most notable feature is the red gem attached to its head by a wire. After repairing itself and absorbing a number of nanites, it took on a monstrous, almost organic looking form bearing little resemblance to its former self, the only recognizable element being the disruptor gem. It has several tentacle-like appendages as well, and a large vertical mouth at the center of its body surrounded by two layers of sharp teeth.
- Tails Doll is based off the character from Sonic R.
- The Tails Doll made a cameo in the first story of STH #134, at a concert of Mina's.
- Writer Karl Bollers intended to use Tails Doll as an antagonist in the series following Sonic's year long absence in space. Tails Doll would have been built by an amnesiac Nate Morgan to serve Metal Sonic. The plans were dropped after Bollers left the comic following STH #134.
- Many people make up violent stories about Tails Doll on the Internet. His scary nature appears to be reflected by some off-panels where it scares Tails or Cheese while Cream isn't looking, it was evidenced even further in a recent "Sonic-Grams", in which the person answering the letters said he couldn't mention how Tails Doll would impact the story because he was "too scared". This may also have been the inspiration for Tails Doll's transformation into a monstrous being.
- The Complete Sonic Comic Encyclopedia lists the Tails Doll as a similar model to the Metal Series but states that it is 'not a true Metal'. It even states that Tails Doll is "more like an insult to Tails."