While serving aboard Enterprise, he was friends with an officer named Tom who was ship's barber until his death in the Expanse. After that, Jimmy took over that position which he was training for under Tom.
While in Main Engineering, a spatial distortion risked a loss of containment in the warp core. Luckily, Jimmy quickly thought to plug a hole with his sweeper saving the ship, but his legs were severed in the process.
He later woke up in Sickbay, where he vomited as Dr. Phlox gave him a grim report. Captain Archer assured him that he was a hero and saved the ship, and that he'd get a medal. Before drifting off to his final sleep, he was pleased that he'd be able to tell his mother in Heaven that he was a hero. (ENT short story: "Hero").