SpoilerShe was first introduced during the Android Arc (episodes 69-71, manga chapters 140-146). Tama has long green hair that is tied in a braid and has a "mole" in the centre of her forehead that is actually the switch to power her on. However due to this "mole"-like switch, she used to be teased and called "Black Mole Beam" by her other robot peers.
She was first found as a disembodied robot head by Gintoki when he was trying to collect his old JUMP issues from the garbage dump in the middle of the night. Gintoki fainted when he saw her, but when he woke up the next morning, he discovered that Kagura had brought the head to their house and was using it as an "egg-cracker". When Shinpachi came, however, he correctly identified her as Etsuko-chan, a popular android model in the market then.
Tama was then named by Kagura, who was obsessed with eating egg on rice at the time. She also seems to have some rather strange main functions, such as imitating the Dragon Quest RPG.
In fact, Tama was originally a robot created by Professor Hayase, to provide his sickly daughter with a companion. Hayase tried to implant the personality of his daughter - Fuyou - into Tama, but the experiment killed his daughter in the process. Tama however, possesses the element known as the "Seed", and therefore retains some of Fuyou's personality and is capable of human emotion.
When Tama was first found, she had lost her memories prior to becoming only a head, and was at that time framed for the murder of Professor Hayase. When she regained her memories later, it was revealed to the Yorozuya members that Hayase had already died when he tried to implant his own personality into another robot, Robot 502.
The android Hayase later began a robot uprising, even hijacking the Terminal, in order to retrieve the Seed and Tama, whom he saw as the copy of Fuyou. The Yorozuya members and Tama soon became embroiled in the fight, and at the end, to allow her newfound friends to escape the collapsing Terminal structures, Tama ultimately sacrificed herself to save her newfound friends.
Nonetheless, her head was preserved by Gintoki, and Shinpachi and Kagura found her data amongst dozens of other robots' data from the ruins of the battlefield. Despite reconstructing her, Tama had already lost most of her memories during the showdown at the Terminal. She however, still remembers one thing: that samurai are in a class "above Hero and Demon King", and are her friends. This had been her earlier conclusion after having been saved by Shinpachi while being chased by killer maid robots.
Seiyuu: Minami Omi