A Tails Doll is a new kind of Badnik, masquerading as a harmless children's toy. Its appearance in Sonic the Comic Online gives them something of a more well put-together design compared to the roughly stitched together design in Sonic R, but it is still recognisable as being the same character. Like the Troopers, a Tails Doll has no organic battery, instead deriving its power from the glowing red gem on its forehead which is blue when the doll is inactive. The gem enables the Tails Doll to manipulate gravity in a number of ways, as Amy Rose and Sergeant Tin found out the hard way, such as downing projectile weapons before they can hit, forcing enemies down or into the air, and levitating themselves. One doll on its own shouldn't be too much of a problem for someone capable, but if Monsters on the Miracle Planet is anything to go by, the dolls seem to operate in packs.
Given Tails' new status as the hero of Mobius, it makes sense that the children of Mobius would have toys of him, and at least 3 inactive Tails Dolls were brought onto the Miracle Planet by the kids during their evacuation. Once they had activated and commenced their attack, they gave Amy and Tin a hard time with their strange abilities. Amy was only able to take the dolls out with a well-aimed shot from her crossbow which struck all three dolls' gems, shutting them down. There are still plenty more on Mobius though, hiding in plain sight, waiting to be activated..