Gallaxhar (voiced by Rainn Wilson) is the main antagonist of Jaden's Adventures of Monsters Vs. Aliens. Gallaxhar was seeking the most powerful substance in the universe called "Quantonium." When it ended up in the body of Susan Murphy, or Ginormica, he sent a robot probe to retrieve it. After Ginormica, Jaden and his friends destroy the probe, Gallaxhar traveled to Earth to retrieve the Quantonium himself. He abducted Ginormica and took the Quantonium from her to build his army, and conquer the Earth. But when his ship was set to self-destruct, and Ginormica took the Quantonium back, he was defeated.
- Gallaxhar will become Jeffrey's enemy in Jeffrey & Friends' Adventures of Monsters vs. Aliens. From then on, he'll become one of Jeffrey's recurring foes.
- Gallaxhar will return for revenge in the Jeffrey & Friends are Home Alone trilogy and the Jeffrey, Jaden & Friends meet Indiana Jones saga.