Seymour was a constant presence in early Spider-Man stories by Stan Lee and Steve Ditko. But he was a very minor character, seldom seen without Flash Thompson. Many of his appearances give him no name. His first name was revealed in "Amazing Spider-Man" vol. 1 #17 (October, 1964). His last name was revealed in "Marvel Knights Spider-Man" #8 (January, 2005), three decades following his first appearance and an issue following his death.
According to flashbacks in "Amazing Fantasy" #17 (January, 1996) Seymour and Peter Parker were friends during their childhood years. He is depicted as one of the guests in the 11th birthday party of Peter. They started drifting apart while attending junior high. Peter had started developing into a science nerd, Seymour was more interested in social gatherings. They both enrolled in Midtown High School.
There Seymour met his idol: Flash Thompson. Eugene was loud, funny, energetic and popular. Seymour wanted to be just like him. He started hanging out with Flash and imitating him. Flash took an instant dislike to the "bookworm" Parker. So Seymour followed Flash's lead in belittling Parker at every opportunity. In contrast to other high school bullies, Seymour was verbally abusive but mostly avoided physical fights.
In a flashback in "Amazing Spider-Man" #17, Peter was getting beat-up by Ernie (1983). Seymour was depicted observing from the sidelines and taunting Parker as usual. The beating was interrupted by C. J. Vogel who got everyone laughing with his jokes.
Seymour made his first actual appearance in "Amazing Fantasy" #15 (August, 1962). Peter Parker was attempting to act friendly by inviting some popular kids to join him for a visit to the Science Hall. Seymour replied by driving away with two pretty girls. Taunting Peter with the following phrases: "You stick to science, son! We'll take the chicks!" and "See you around, bookworm!"
Seymour next appeared in "Amazing Spider-Man" vol. 1 #4 (September, 1963). In that issue, Spider-Man fought Sandman within a Midtown High classroom. Several students were present as bystanders. Flash Thompson cheered for Spidey. Seymour followed his example by also cheering for the vigilante: "Give'im one for us, pal!" Spidey was bemused to find his tormentors cheering for him. Later, that issue, an enraged Peter Parker challenged Flash to a fight. He realized what he was doing in time to back down. Seymour was seen laughing at the "cowardly" Parker. Another student actually bothered to touch Parker's arm and noted that "puny" Parker actually had "muscles like a weight lifter".
In #5 (October, 1963), Flash Thompson dressed up as Spider-Man to play a prank on Peter Parker. Seymour assisted him by helping locate Parker. He was eager to witness the encounter, commenting "Betcha he'll jump out of his skin when he sees Spider-Man! This'll be the greatest gag of the century!" He then rushed to alert Flash that Parker was approaching. Unfortunately for them, Doctor Doom was searching for Spidey at the time and had estimated his general vicinity. Victor failed to notice Peter Parker in plain clothes and instead abducted the costumed Flash. Seymour did not intervene to protect his idol from the Latverian monarch.
In #8 (January, 1964), Peter and Flash kept arguing, interrupting the science class of Mr. Warren. So he arranged for them to settle their feud in a boxing match at the gym. Seymour was the one helping Peter put on his boxing gloves. Seymour's smirk was evidence of his thoughts on who was going to win. Then he rushed to the side of Flash, suggesting "Don't end it too soon, Flash boy! Give us a little show, huh?" During the match, Parker delivered a knock out punch on Flash. But Thomspon had been distracted by a shout alerting students that the Living Brain was out of control. Seymour shouted his frustration: "That was a crummy thing to do, Parker! Poor Flash wasn't even looking!"
Later that issue, Flash had returned to consciousness. Just in time for a couple of escaping criminals to trip over him. They were knocked out. Seymour was one of several students surrounding Flash. Wondering how did Flash manage to do that. Peter seized the opportunity to point several clues that Flash was Spidey. A confused Flash was left surrounded by several people viewing him in a new light. Seymour included. (The issue first depicts Seymour with light brown hair, later with red hair).
In #9 (february, 1964), Peter was concerned with the health problems of Aunt May. At school, Peter was lost in thought, ignoring any taunt from his classmates. Seymour thought Peter was acting as a snob: "S'matter, teacher's pet? Too busy to answer us common folks?" Walking out in a daze, Peter also ignored a friendly gesture from Flash.
In #12 (May, 1964), Seymour only makes a couple of silent cameos. Standing right next to Flash on two different occasions. "Untold Tales of Spider-Man" #11 (July, 1996) features a retro story directly following that issue. Seymour is depicted giving a class presentation. His subject seems to have been a fishing trip that Seymour had taken with his grandfather.
In #13 (June, 1964), Mysterio was framing for a series of crimes. The press and public had turned against Spidey. Even Spider-Man himself had started wondering if he has split personality. In Midtown High School, Flash found himself the only one willing to defend his hero. Several boys questioned Flash on his belief that Spider-Man is innocent. One of them seems to have been Seymour, for once not on the same page as his idol.
In #14 (July, 1964), Liz Allan had heart Flash dismissing Peter as an egghead one time too many. She let her annoying boyfriend have it, by pointing out: "It so happens, Mr. Flash Thompson that you couldn't be! You don't have the equipment for being an egg-head! Namely, you're too dumb! It's the men with brains who run this country -- not muscle-bound goops like Y-O-U!". Flash was speechless. But two members of his gang easgerly sided with Liz on this one. Seymour seems to be one of them. (So much for loyalty).
In #15 (August, 1964), Kraven managed to use on of his potion on Spider-Man. The following day, Peter Parker was attending a science class. When his hands started shaking, an effect of the potion. His classmates soon noticed, a Seymour-like figure asking "Hey! What's with Puny Parker??" As Peter caused a mess in the lab, Seymour started whispering on the ear of Flash: "Looks you were right about teacher's pet, Flash! He's Finally crackin'up! ... If you ask me, he's all shook up since you told him you'd paste'im one if he didn't stay away from your girl Liz! You know what a coward he is!".
In "Amazing Spider-Man Annual" #1 (1964), Flash challenged Peter to a fistfight in the middle of the street. Seymour and other boys were encouraging Flash. But the fight was interrupted by the ectoplasmic form if Doctor Strange. Peter had just enough time to avoid a direct punch from Flash. Thompson accidentally punched the ectoplasm. He was left severely spooked, while his gang was impressed with Strange. The same issue has a pin-up of the Midtown High supporting cast. Including Flash flexing his muscles for male and female admirers. Apparently including Seymour.
In #17 (October, 1964), Flash Thompson had organized the first meeting of the Spider-Man Fan Club- Forest Hills Chapter. The event was to be held at the Avenue Dinner Club, owned by the father of Liz Allan. Flash had promised everyone that Spidey would attend the event. Counting on Spider-Man not wanting his fans disappointed. A larger than expected crowd turned up. Seymour started worrying that the hero won't make an appearance. Flash remained confident. Spidey did arrive in time. but the event was crashed by Green Goblin/Norman Osborn.
In #18 (November, 1964), New York City was reacting to news that Spider-Man had run away from his latest battle with the Green Goblin. Which had taken place in public. He was actually reacting to news of a medical emergency of Aunt May. But now the public, other heroes and even the villains regarded him as a coward. The only one still loyal to Spidey was Flash. When Seymour had the nerve to call Spider-Man "a professional coward", Flash threatened to punch out his friend. (Curiosity: Kraven is the only other person to not judge Spider-Man. He still hopes to locate Spidey to have his vengeance.)
A few nameless friends of Flash Thompson make appearances over the following issues. But none stands out from the crowd. Seymour and his bow tie return in #25 (June, 1965). Flash Thompson is trying to impress a hand full of girls. When a smiling Seymour points out that Liz Allan, Flash's main love interest, is once again running behind Peter Parker. As intended, Flash is pissed. Flash later gives chase to Parker with four other boys joining him. One of them seems to be Seymour.
In #26 (July, 1965), Peter Parker arrived at school just after a shouting match with Betty Brant. Who was at the time his main love interest. He was in a particularly foul mood. Flash Thompson chose the wrong moment to start his tauntings again. Peter insulted Flash and dismissed his friends, including Seymour, as a "gang of grinning hyenas". Flash threatened Pete with a beating. Pushing Parker over the edge. He tackled Flash, Seymour and two other boys. With a shocked Principal Davis observing the fight. Liz Allan , love interest to both Peter and Flash, intervenes to stop the fight before anyone gets hurt. She is shocked to see Peter and Flash still shouting threats at each other. She was mad enough to severe her relations with both boys.
Later, Davis summoned Parker to school. The friends of Flash were hopeful that Peter would get expelled. Seymour gleefully observing: "Hah! What a cryin' shame! We sure will miss Puny Parker around here!" But Flash left them behind. He wanted to visit the Principal and take part of the blame in the fight. Flash was one person who didn't want "Puny Parker" expelled.
In #28 (September, 1965), the senior class of Midtown High graduated. With Peter and Flash winning scholarships to Empire State University. An enthusiastic Seymour commented "Boy! The chiks'll go ape over ol'Flash now!" Like most of the Midtown High characters, Seymour was written out following this issue.
Reunions and Death
Seymour next appeared in "Amazing Spider-Man Annual" #17 (1983), attending his high school reunion. He stuck a "Kick me" sign on the back of another guy. Who turned and punched him in return.
He attended another reunion in "Marvel Knight Spider-Man" #7 (December, 2004). He got together a few other former bullies and provided a plan for them. They would give Pater Parker a wedgie and gain photographic evidence. Then present the photos to Flash to cheer him up. (Flash was paralyzed and depressed at the time.) When attacked, Peter easily fended them off. But then Venom/Angelo Fortunato attacked them all. Most of those present were simply knocked out. But Seymour stayed awake and heard Angelo identifying Peter as Spider-Man. Seymour was shocked to learn that secret after so many years. But then Venom noticed him and moved to remove the bystander. He easily broke Seymour's neck, killing him.
In #8, Peter and his wife Mary-Jane Watson-Parker were asked to testify for the circumstances surroundimng Seymour O'Reilly's murder.