Longbourne is one of John Silver's gang of intergalactic pirates recruited to serve aboard the spaceship RLS Legacy in her expedition to find the legendary treasure of Captain Flint. He is a lanky purple alien creature of unknown species with a long body, purple skin, gray belly, six limbs (four legs with clawed feet and two arms ending on tridactyl hands) and a pair of eyeballs contained inside his wide mouth. When Silver led the mutiny following the Legacy’s arrival on Treasure Planet, Longbourne along with Hands and Fayvoon, pursued Dr. Doppler, Captain Amelia and Jim Hawkins as they attempted to escape in one of the lifeboats. Thanks to Doppler's unexpected targeting ability, the three pirates ended up falling out of the ship's longboat room from a great height to their apparent deaths.
- He is voiced by Denis Leary.