In the anime episode For Ho-Oh the Bells Toll!, he was portrayed as being a proud and arrogant person with a slight superiority complex and exhibiting an obsession with Suicune, challenging Ash for daring to say that he had met the Legendary beast. This might just have been a form of jealousy on his part, for Ash had also seen Ho-Oh as well, while he had yet to encounter any himself. In the same episode, when he finally saw Suicune, he tried to catch it partially for ego gratification, ironically making him no better than the people who he had mentioned were unworthy for it. However, for some reason when he appeared in The Legend of Thunder! he mentioned Suicune only once, and then only in reference to the other beasts. This is only in the Japanese version, however. In The Legend of Thunder!, Eugene[note 1] assisted Jimmy, Marina, and Vincent in their battle against Attila and Hun. Marina fell for him because he wore a cape, though he does not allow anyone to touch said cape. Eugene is also much differently portrayed here than in his original appearance. He acts as an elderly father like supervisor to the children and is quite calm in most situations, even when Jimmy and Vincent were panicking over Marina being kidnapped. He also drove a red SUV which was accidentally destroyed by Raikou during the final battle with Team Rocket.

He is apparently very close friends with Morty, who is also an expert on the Ecruteak legends. Morty acts as Eusine's voice of reason, trying to convince him to calm down and ease up, but to no avail. When Eusine left suddenly at the end of the episode, Morty's lack of surprise indicates that this has happened before. Eusine is also good friends with fellow researcher Kudo and is sometimes described as a "Champion Scientist".
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