S1·E56 The Great Brain Robbery

Spectra attacks the Artificial Brain Center on Earth and steals a top-secret "Brain of Evil". The Team tracks down the stolen brain, only to be attacked by the Brain Mecha and then Spectra Pirates! G-Force returns with a piece of the Mecha to Center Neptune, and then attends the Annual Robot Show the next day, just in time to watch Spectra steal the new "Fembot" to use as a body for the Brain of Evil. Mark sneaks into the Spectra base while the rest of the team goes after the Brain Mecha.