Although the Generation III games show there to be at least two Magma Admins, only Tabitha ever appeared in the anime. His first appearance was in A Three Team Scheme!, where he led a group of Magma grunts in an exploration of some ancient ruins on Dewford Island in search of the Cave of Origin. They also had a confrontation with Team Aqua. Due to a dubbing error, he was mistakenly referred to as "Field Commander Harlan" during this episode, though his name was corrected in all subsequent appearances.
Tabitha appeared again in The Spheal of Approval. He and two Magma grunts broke into the Oceanic Museum in order to steal a rock sample owned by Captain Stern. Although Ash and his friends attempted to stop them, Team Magma successfully made off with most of the sample.
In Fight for the Meteorite!, Tabitha led a squad of Magma grunts on a mission to Mt. Chimney, first stealing a meteorite from Professor Cozmo and then using it to power an experimental machine affecting the volcano. However, their plans were ultimately thwarted by Ash and Cozmo.
His final appearance was in Gaining Groudon and The Scuffle of Legends. His submarine accidentally picked up Ash and his friends while out on patrol, bringing them to Team Magma's base. He was present for the battle between Kyogre and Groudon, and like the rest of Team Magma, has not been seen since.