Here are some definitions I've found -
"The stereotypical fanboy can be seen as the thirty-something guy at comic conventions with a goatee or beard wearing some sort of comic book or fiction-based t-shirt. He still lives at home with his parents, usually in the basement. For a good representation, watch the comic store guy on the Simpsons. For the most part fanboys are good people with a devotion to their hobby. But Star Wars fanboys are a completely different species.
i.e. A Star Wars Fanboy would notice Luke's light-saber in the movie poster is white when it's actually green onscreen. Even though it has nothing to do with the overall story they would somehow see this as detrimental to their enjoyment of the movie.
Star Wars fanboys are so anal in their outlook that they believe they know better than George Lucas and anything that the Star Wars guru does is somehow wrong."
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fangirl: See fanboy 😉 No, okay, seriously, any childish, obsessed, over-the-top fan who makes more mature fans embarrassed to be associated with them. The kind you see on TV (usually in full costume) every time the local newsteam decides to go cover a convention. Specifically, in ficdom, a writer whose stories are nothing but badly-written wish-fulfilment fantasies.
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"You're typical fanboy comment "Jar Jar sucks. Lucas should have made him part machine and given him some kind of bazooka". If you read this and thought "that's a great idea" then I'm sorry, but it's too late for you."
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I couldn't find the good definition. Was anyone else sent it? It started "Fanboys are selfish creatures". Or you could go to TFN forums which are full of them. Look under the topics titled " Could Boba Fett beat the Predator" or " Does Lucas read the fans ideas?".