some idea of how they would be introduced into the show, starting as a background character and only becoming a significant figure by the midpoint of the first season. Though they had some idea of the Observers' role, they gave Cerveris much leeway to develop the character in the manner he wanted, from choosing the outfit he would wear to his language mannerisms. Cerveris further is credited with creating the written Observer language during his scenes in "The Arrival", which the production team later extrapolated into a complete language for the show. Shapeshifters Shapeshifters are androids from the parallel universe, possessing superhuman strength and damage thresholds, and acting as soldiers in the war between the universes. They are able to take the form of any person by using a device that plugs into the roof of their mouth and the mouth of the target. This process occurs after the shapeshifter has killed the target prior to the transformation; without the device, the shapeshifter is locked in its current form. Shapeshifters also may be programmed as sleeper agents, unaware of their unusual nature until they are activated. The primary characteristic differentiates a human and a shapeshifter is the large quantity of mercury in their blood, and the presence of a metallic data disc at the base of their spine. William Bell believes the shapeshifters were designed this way to withstand travel between the universes. The first shapeshifter witnessed by the Fringe division is one that follows Olivia after her meeting with William from the parallel world in the second-season premiere, "A New Day in the Old Town". He eventually kills Charlie and takes his place, using his position to find the location of Newton before he is identified by Olivia and killed. Several other shapeshifters have been shown in the series, including one that aids in the parallel universe's Olivia's escape from the prime universe. Peter Bishop later takes it upon himself to kill all of the remaining shapeshifters in the Prime Universe, after he is able to decode their sleeper identities from the files on Fauxlivia's computer. He successfully kills all of the ones identified, but it remains to be seen if he eliminated all of them. Thomas Jerome Newton Thomas Jerome Newton (portrayed by Sebastian Roché) is a leader among the shapeshifters and the main antagonist of Season 2. When Olivia is transported to the parallel universe, she meets