He was voiced by Jeff "Swampy" Marsh.
Mantel became involved in the abducting of Milo Murphy by his fellow Octalians. As it turns out, the Commander intends to deliver Milo to their home planet to utilize his negative probability ions for unknown purposes.
However, Murphy's Law caused many glitches in the ship, allowing Milo to escape through the ventilation systems. The Commander then sets out Mantel and several of her soldiers to go into the vents and capture Milo, but Murphy's Law only made things even worse as they end up being trapped in serious situations that they are unable to escape from.
Fortunately, Milo arrives to the rescue by using his backpack to provide solutions to free Mantel and his cohorts from danger, and they explained the events to the Commander, who decided to transport Milo to their homeworld for some obvious reason. Unfortunately, Milo's ions caused the ship's main console to malfunction, causing their ship to crash towards Earth. While Milo is accidentally jettisoned from the ship due to decompression (though he is saved by Doofenshmirtz, Zack and Melissa), Mantel is forced to leave on an escape pod with his fellow Octalians to avoid the collision.
It later turns out that the Octalian planet is being threatened by a sphere of negative probability ions surrounding the Commander's daughter Orgaluth, and that the Commander only needed Milo's help due to his knowledge in Murphy's law. Realizing this, Milo brings in his friends (including Heinz Doofenshmirtz) to help out in containing the sphere by distributing the ions to every Octalian, thus averting the crisis for good. It can be implied that Mantel is relieved along with the other Octalians that their planet is safe once again.