"Mischief" (aka "Pink Guy")
"Mischief," as referred to by fans (due to lack of an official name) is a recurring character in the Interface series and is a key player in the plot.
Origin
"Mischief" is believed to originally have been an American Human within the US Navy, although his form was altered by his involvement in the 1943 Philadelphia Experiment. The Experiment has been subject to much speculation and conspiracy. Within the Interface universe, the Ship was teleported from Philadelphia to New York. The process caused rather negative effects, like the crew fusing to the hull. "Mischief's" previous being was destroyed in the experiment, and instead became the creature he appears as now.
Physicality
Although "Mischief" appears mainly as a pink, sepertine creature, they are known to take many other forms such as a bus or a "beautiful sunflower". It is believed that this shapeshifting power may have been gained through Cerebral Electricity, a mysterious energy which appears throughout the series. It is unclear the full extent of the power gained by "Mischief" through use of Cerebral Energy, nor how many possible forms they might take.
"Mischief" taking form of a Bus (Ep 02 of Interface)