Eustace Strych is an antagonist in The Adventures of Jimmy Neutron: Boy Genius. He appears in the episodes "Billion Dollar Boy", "King of Mars", "The League of Villains" and "Jimmy Timmy Power Hour 3".
He was voiced by legendary voice actor Rob Paulsen.
Eustace first appears as the main antagonist of the Jimmy Neutron episode Billion Dollar Boy. He is an archenemy of Jimmy Neutron who seeks to humiliate him. He first appears in the episode as a competitor in the Retroville Kite-Flying contest only to find himself losing to Jimmy when he shoots his kite down out of the sky. Cindy Vortex starts to have an attraction to Eustace as he invites Jimmy and company to his mansion for a banquet. After a while, Eustace challenges Jimmy to use his dog Goddard against a robot adaptoid that attracts to whichever weapon Goddard uses. He is then defeated when Goddard plays dead and his prototype blows up. Eustace then swears to pursue Jimmy with everlasting vengeance against him. He then finds himself taken to his room via his butler being ordered by Eustace's father to use a claw machine on him to have him sent to his room to think about what he's done after Eustace completely loses it.
Eustace next appears as the main antagonist turned anti-hero of the episode King of Mars. He and his butler are first seen attacking Jimmy and his friends via a bug-shaped Tripod ship while attempting to remove him of his property. Jimmy manages to defeat Eustace and his butler who fall into unconsciousness after a brief battle. Eustace then plots to defeat Jimmy while on Mars and discover a special power source hidden within Mars itself. He is then seen in space via his tripod ship again giving a speech of his evil plan to become the 'first King of Mars'. Eustace then kidnaps Cindy in an attempt to get Jimmy's map. He then chases Jimmy to the power source only to find himself, Jimmy, and Jimmy's friends captured by rogue Martians. Eustace then forms an uneasy alliance with Jimmy to save the Earth and they successfully return to Earth with the Martian's power source. However, this doesn't stop them from being arch-enemies.
Eustace is next seen as a supporting antagonist in the episode The League of Villains. He is first seen in the episode with the villains King Goobot V, Professor Calamitous, Beautiful Gorgeous, Grandma Taters, the Junkman, Baby Eddie, and the three Space Bandits plotting their revenge on Jimmy Neutron for foiling their individual plans to destroy him. He is then partnered with Prof. Calamitous to trick Jimmy's friends into dancing for approximately 15 minutes through a CD. He is then seen as a part of the circle surrounding Jimmy laughing at him. Eustace is next seen as part of the Jury that Goobot precises to verdict against Jimmy. He is next seen fighting with the villains against Jimmy and company who are blasted into a ditch where Junkman shoots them into. He then is disgusted by a gross love relationship between Beautiful Gorgeous and Junkman while the other villains are also in disgust. Eustace then runs away from Eddie who threatens him by making him change his diaper. He is last seen in the episode when the villains travel through a wormhole while following Jimmy and company back to Retroville which was transported back in time to the Cretaceous era. He along with the other villains face defeat when Jimmy blasts Goobot and the others into an indestructible force field.
Eustace's final appearance is in the (non-canon) Jimmy Timmy Power Hour 3 as a minor villain. Still wanting revenge, Eustace appears in his tripod ship once more against Jimmy (only this time Jimmy has Timmy Turner, Cosmo and Wanda alongside him). Eustace attempts to finally get rid of Jimmy, but he is quickly defeated when he is given chicken pox and sent directly to jail for his actions against Jimmy.
Eustace is a rich, snobby, greedy, petty and sadistic boy with a disturbing evil laugh. He was only using Cindy's love to emotionally crush Jimmy and then force Jimmy to watch Goddard die.
Eustace appears as a well-groomed boy with a bathrobe and stylish hair.
- Since the Fairly Oddparents crossovers are non-canon, he is still trapped in prehistory.