His original tweet garnered a massive response from fans of the animated franchise and the live-action movies.
Some fans even tried to get hashtags like "#ReleaseTheGunnCut" trending. Others admitted they had always liked the idea of a romantic relationship between Daphne and Velma.
"You're telling me there's footage of an ambiguously gay Velma Dinkley hidden away in the Warner Brothers vault that may never see the light of day???" asked one person.
Tweeting to the fan, Gunn wrote some of the previous footage was available to watch in the deleted scenes, which were included under the film's special features upon its DVD release.
"Hey, you tried. A for effort James. Those studios are too dumb to get out of their own way," added another user.
"Damn dude the studio didn't have to do you dirty like this. I got hella gay vibes from her towards Daphne," tweeted a third.
"Maybe one day a third film will happen but thank you for trying your best to make it happen," chimed in a fourth fan.
Some folks just wanted Gunn to help make a Scooby-Doo 3 film happen with the original cast returning.
According to The Independent, Gunn was not the only Scooby-Doo writer to try and make Velma gay. Tom Cervone, who directed the recent animated movie, Scoob, also commented on her sexuality recently.
On Instagram, he stated that they intentionally made Velma act "a little off and out of character" when she dated Shaggy. He also said that they felt Velma was a lesbian and not bisexual.