Eliza Dushku -- Sexual Fetish Gurus Not Impressed ... You Gotta be a Furry to Roll With Us!

Eliza Dushku attended her very first furry convention, but according to the organizers that doesn't mean she's automatically in the sexual fetish club.

"Uncle Kage" -- the organizer of Anthrocon -- tells TMZ he had no idea Dushku even attended Anthrocon in Pittsburgh over the weekend. In case you weren't aware, Anthrocon is the world's largest convention for those fascinated with furries ... well, just Google it (NSFW).

Kage isn't fully on board with extending a special invite to Eliza for next year's convention. He's not convinced she's fully committed ... just because you hang out with furries, doesn't mean you are one.

He explains, "We do not bring in celebrities simply for the sake of having celebrities."

Gotta step up your game and get a fursuit, Eliza. The furries will be watching ...