Captain "Sparks" Sweeney was a member of Parry's Old Guard
Sweeney was a member of Parry's Old Guard, marines who went on dangerous military missions, fourty years ago. According to Drake, he's been to some of the darkest places imaginable, an is a very dangerous man. He had a progressive myopia disorder and was close to being discharged, but an army research team implanted devices in his head that would help to fix his eyes and ears. However, his senses were boosted too much, so just the tiniest noises and smallest amount of light hurts. Anything with an electric currents also messes with the wires in his head. Because of all this, he has to live without electricity or heat.
When Drake's mother died, Sweeney and a few other Old Guard troops helped Parry to take care of him. Drake described the group as "A bunch of extremely strange but incredibly interesting uncles" and looked up to them.
During the war against the Styx, Drake, along with Will and Chester, find an aged Sweeney, asking for his help, along with Professor Danforth and Jiggs. Sweeney joins the team soon after. When Parry's estate is evacuated, Sweeney accompanies Drake and Will to help draw the Styx away. They soon meet up with Eddie and his Limiters, whom try to join the group. Sweeney knocks out two of the Limiters, helping to even the odds a bit. After Eddie reveals Bartleby's fate, he stops Will from killing Eddie, then orders the Limiters to give him a proper burial.
With his super hearing, he overhears almost the entire conversation about The Phase. They travel to The Complex to make plans with the others on how to stop it.
He participates in the assault to stop The Phase, joining with the rest of the Old Guard.
He is trapped in The Complex with the rest of the group during Danforth's betrayal. During one of the days being trapped he seems to be very drunk. He later helped the group to escape, then travels to the Colony to help Drake and the rest of the group end The Phase. They travel to the inner world; after he helps plant the nuclear bombs, the party is attacked by Rebecca One and the now mutated Vane, whom he keeps taunting. During the ensuring fight, he attacks and picks up Vane, telling the Limiters to back off or he'll kill her. When the nuclear bomb detonates, the explosion overloads the circuits in his head, causing his head to explode. His death also causes Drake's virus to be released, killing the remaining Styx in the inner world.
- Sweeney enjoys calling the Styx "stickies." He also likes to call the Styx Warrior Larva "Sticky Bugs."