Ice-T (also known as Tracy Lauren Marrow), is a well-known human rapper on Earth, who is actually an ageless wandering alien from the dawn of time known as Water-T.
Before the events of "Get Schwifty", Ice-T's life on earth can be assumed to have been fairly similar to the real world version of Ice-T, in which he was a famous rapper.
After a Cromulon falls to earth Ice-T is the sole survivor of a catastrophe at the Grammys that kills all of earth's (good) musical artists. Upon hearing of Ice-T's survival The President orders that he be brought to Area 51 to help impress the giant head. Though he does not arrive in time to quell the head before Rick Sanchez can, he does appear before Earth is set to perform on Planet Music.
After giving a poor effort in composing a song to save the earth Ice-T reveals his true self to Rick. Ice explains that he is actually an ancient alien from the dawn of time who was exiled from his homeworld of Alphabetrium due to his intense apathy of everything. Since this time he has drifted from world to world, not caring about anyone or anything. Rick tries to reason with Ice-T that he can't live without purpose forever, but Ice is unmoved and flies away from the earth to avoid its imminent destruction should Rick fail.
After a rogue nuclear launch the cromulons decide to fire a deadly plasma ray directly at the stage, intending to destroy the earth. At the last moment Ice-T flies in front of the ray and deflects it from the earth with his body, saving the world. As his body breaks apart under the ray he tells Rick that he was finally inspired to care from him, and his stalling allows The President and Morty Smith to reach the stage and sing their song. After the world is saved, Ice-T returns to Alphabetrium, where word of his sacrifice has spread. Back on Alphabetrium Ice-T meets with the world's elders, which include his father. Agreeing that his actions on earth have shown he has changed, his exile is lifted. He regains his true form as Water-T. At this moment their world comes under attack from the Numbericons and his father dies from a ceiling collapse. Despite overwhelming enemy numbers Water T pulls out his guns and bursts through the doors, ready to crunch the numbers.
In his natural form, Water-T is a large capital T composed entirely of water. Before his return to Alphabetrium he was long imprisoned in the form of a spike of ice and took the name Ice-T.
His Ice-T form was shown to be spectacularly resistant, deflecting a blast from a plasma ray strong enough to annihilate the earth. This durability might explain why he survived the catastrophe at the Grammys. Ice-T was also an impressive shapeshifter, which he used to blend into the worlds he inhabited along his travels.