Mouse (played by Matt Doran) is a crew member of the Nebuchadnezzar in The Matrix.
In the film, Mouse is the youngest crew member of the Nebuchadnezzar and the programmer of the virtual reality training simulation program. One of his stand-out scenes occurs when he is discussing to Neo whether the Nebuchadnezzar's food tastes like "Tastee Wheat" (a brand of cereal, posters of which can be briefly seen in the train stations shown in The Matrix Revolutions), and adds to the theme of subjective reality by suggesting that the flavor associated with both is not the 'true' flavor, but the Machines' error. He is the creator of the program Woman in the Red Dress, which is used as a distraction part of Neo's training. He is a very eager young man, excited to see the possibility that Neo could be the one to end the war. He also appears to be something of a hedonist, as he offers the Woman in the Red Dress to Neo and later says, "To deny our impulses is to deny the very thing that makes us human".
Mouse is the first victim of Cypher's attempt to betray the crew in order to return his body to the Matrix power plant. As Agent-led SWAT team members storm the building used by Neo and the others as an entry/exit point, Mouse attempts to stop their initial approach wielding dual automatic shotguns (custom made for the film), but is gunned down by the police.