The Sallybot is a near-perfect robotic doppelganger of Princess Sally, created by Snively for the purpose of infiltrating the Knothole Freedom Fighters and locate Knothole for Dr. Robotnik. When the Sallybot got to Knothole, however, Tails was able to detect that she was not the real Sally. Rotor then reprogrammed her and made her turn on Robotnik and Snively.
Sally was captured, prior to detonating the explosive canisters that Sonic spread around Robotropolis. Instead of immediately roboticizing her, however, Robotnik had Snively build the Sallybot. They used the roboticizer to give the Sallybot Sally's appearance, and to copy the basics of Sally's personality and some of her memories into the robot. The Sallybot was then placed in a cell and “rescued” by Sonic.
Taken back to Knothole, she runs into no problem fooling everyone but Tails (as she is apparently missing several key memories dealing with him). First, she is unable to properly administer the "funny kiss" until told where the kiss is. Second, she doesn't recall the proper book to read to Tails, then she reads the proper book in a completely monotonous and hurried tone, as if stressed or tired. Finally, Tails sees her eyes glowing red. She/it sabotages the garden and convincingly acts surprised when the others discover something wrong with the garden. She accompanies Sonic, Bunnie, and Rotor to finish the job that was started when Sally got captured. Tails warns Sonic, who assures him that "Sally" has had a rough day and was probably just under a lot of stress (Sonic outright dismisses the glowing eyes as Tails perhaps being tired and imagining things).
After accidentally knocking Sonic down, she fails to properly perform the Freedom Fighters' secret handshake and is confronted by Sonic. Instead of fighting him outright, she pushes him down and runs off. She then, proceeds to set a trap by excreting mega-muck from one of her fingers. Sonic run into the trap and gets stuck. Before Sallybot can attack, however, she is knocked down by Bunny. Sonic then proceeds to run around her, causing her systems to short out as she tries to keep track of where he is.
Rotor opens her back panel and tinkers with her programming, making her disclose Sally's location and also turning her against Robotnik and Snively. Sonic uses her to rescue Sally and leaves her in the roboticizer, in order to fool Snively into not noticing that Sally has been rescued.
After the Roboticizer is activated, it has little effect on the Sallybot, apart from making her eyes glow and giving her a disheveled appearance. She then proceeds to destroy most of the roboticizer equipment in the room. It is unknown what happened to her after this episode.
Having been programmed with Sally's personality, the Sallybot possesses many of Sally's personality traits, but is loyal to Robotnik's cause. However, the Sallybot does not have a complete copy of Sally's personality. Therefore, she acts a bit off or seems a bit scatter-brained and absent-minded when trying to emulate. As her public personality, though she is very adept at pretending to be Sally. She only acts like Sally when in the presence of the Freedom Fighters, however.
When not overtly pretending to be Sally, she is quite cunning. She prefers to have an upper hand in a fight, rather than leave things to chance (as evidenced by trapping Sonic in mega-muck before confronting him). When confused by Tails, she seems to get a bit angered.
After being reprogrammed by Rotor, she is seemingly devoid of personality (though, she does seem to enjoy trashing the Roboticizer room).
Powers and abilities
The Sallybot is adept at using what information she was given from Sally's mind. She is also able to shoot lasers from her fingertips, and to produce Mega Muck from at least one of her fingers. Her eyes are able to produce a red ray that either scans things, or harms plant life. She also has the capacity to transmit info to Robotnik's computers.