He is a silly, naive, gullible nerd, but never nasty or cruel. He was a decent, goofy guy. He was played by Eddie Deezen in the two movies, and by Noah Robbins in the 2016 live performance.
Eugene is a good guy, however, he is always teased by the T-Birds. Though mostly by Doody, Putzie and Sonny; Kenickie and Danny seem to ignore him and appear indifferent to him. Mostly probably because he's not a jock or popular, like Patty Simcox and Tom Chisum.
He is usually seen wearing `nerdy' clothes, conservative, like Michael Carrington on his first day. He's usually seen smiling, but gets serious at times. He - like Francine - speaks with a high, squeaky voice.
In Grease 2, he escorted Michael Carrington though the main hallway. He was speaking to Michael as they walked – loudly and slowly, enunciating - as if Michael was a foreigner who didn’t understand the English language at all. "How long.. have you.. been in.. America??"
Michael was from England… birthplace of English. However, Eugene was never a nasty person - slightly pompous perhaps - but never mean-spirited. He might have thought that because the English accent is so proper and structured, Michael may not have understood the American accent, especially with all of the slang flying around.
It's probable that he was a freshman in Grease because he was still going to Rydell and graduated at the end of Grease 2. He probably knew the T-Birds when he was in Junior High. Rydell students were locals, so most likely he knew them from around town. Grease 2 was his senior year, as he was seen in a graduation gown at the end of the movie.
Eugene Hey Guys!
Davey: (Reads roster) Oh DISASTER!
Goose: What, we blew it?
Davey: No, we made it, but we can't perform in public, we're the worst!!
Johnny: We'll get un-worst!
Goose: We'll get liverwurst!
Johnny: (Whaps Goose on back of head) You're knockwurst!
Davey: Oh, how did we get in?!
Louis: Obviously, they recognized natural talent.
Eugene: (Sneaks up) Everybody made it, they didn't have enough acts!! (Snatches roster, runs)
Johnny: ... Get...!! (They chase)
Eddie Deezen stated online that Dennis C. Stewart and him got along and that Dennis would carpool with him to the set.