|Interests||Stealing any form of energy from unsuspecting planets|
|First Appearance||RoboDexo 3000|
The Energy Thief is a giant alien monster who goes from planet to planet stealing its energy. Its only appearance was in "RoboDexo 3000".
When it came to Earth to drain it of its energy, Dexter tried to fight it off with his Robo-Dexo 2000, but his attempt proved futile and the Robo-Dexo 2000 was easily defeated. Dexter then created an improved version of his RoboDexo 2000 called the Robo-Dexo 3000 to combat it, but it ends up becoming rebellious and goes off to fight on its own and it seems to win the fight until the alien absorbs its energy with its tongue. Dexter then reunites with his trusted Robo-Dexo 2000 and defeats the mighty Energy Thief by using solar panels to reflect powerful rays of sunlight at it, causing it to explode.
- The sounds made by the Energy Thief are the same sound effects used for the TIE/LN Starfighters (commonly known as TIE Fighters) from the Star Wars franchise.
- The design and role of the Energy Thief are possibly inspired by the Angels from the Neon Genesis Evangelion animated series.