I just thought you might like a latte with steamed Austrian goat milk.
What do I look like? An imbecile? Of course I want a latte. I LOVE THE WAY YOU MAKE THEM!
— Agent Stone and Dr. Robotnik, Sonic the Hedgehog
Stone is an average sized man with black hair and brown eyes. He bears visible facial hair. For attire, he is usually seen wearing a black jacket, black shirt and a black tie.
Agent Stone first appears accompanying Dr. Robotnik to investigate the electromagnetic pulse caused by Sonic in Green Hills. He "translates" Robotnik's words for Major Bennington as he asserts dominance and begins the investigation. He is later present when Robotnik analyzes Sonic's footprint.
After Tom Wachowski punches Robotnik in the face and escapes with Sonic, Stone rushes into Tom's house to help Robotnik. He is humiliated by Robotnik for not chasing Tom's truck instead, and Stone takes Sonic's leftover quill before the two depart.
Later, when Tom calls the Green Hills Police Station, Robotnik, Stone, and the other agents are present to monitor the call. Stone also accompanies Robotnik to interrogate a bar patron who encountered Tom and Sonic.
Stone watches as Robotnik remotely pilots his drones to chase Tom and Sonic. After the drones are destroyed, Robotnik begins to vent his frustrations on Stone before noticing Sonic's quill and beginning to analyze it instead.
As Robotnik jams to music and finishes analyzing Sonic's quill, Stone brings him a latte, accidentally sneaking up on him and scaring him. He is then told to prepare "The Prototype".
After Robotnik is sent to the mushroom planet in the final battle with Sonic, he finds a rock that resembles a human face and begins calling it "Agent Stone" as a replacement for his assistant. He throws the rock around while making rock-related puns as he begins to explore the new environment.
Agent Stone is a relatively normal and level-headed man, contrasting greatly with his eccentric boss. He is used to Robotnik's antics and understands him better than most other people. He is very subservient to Robotnik, taking abuse and doing humiliating things for him without question. He also seems to genuinely care about or admire Robotnik to some extent as well, thoughtfully bringing him a latte while he works, for example.