Nathan Fillion's big "Guardians of the Galaxy" cameo may have leaked online days after his appearance in the franchise was confirmed.

[Warning: the article contains potential movie spoilers]

Schmoes Know reports a source close to the production claims Nathan Fillion take on the role of Cosmo the psychic Russian cosmonaut dog. Like Bradley Cooper and Vin Diesel, the actor will be voicing his animated character.

"Cosmo is a telepathic Russian dog in the Marvel Comics universe," according to Schmoes Know. "The character was created by Dan Abnett and Andy Lanning, first appeared in Nova vol. 4 #7. Within the context of the stories, Cosmo is the security chief of the spacestation Knowhere and a member of the Guardians of the Galaxy."

Director James Gunn recently confirmed Fillion's cameo appearance on Twitter, but didn't reveal what character the actor would take on.

However, if the live-action "Guardians of the Galaxy" is a box-office hit, Marvel President Kevin Feige would consider turning it into a franchise, according to Total Film.

"[There are] dozens and dozens of Guardians of the Galaxy storylines - there's a group that came about in the '60s, they were revamped again in the '80s and they changed into this incarnation that you see in this movie about eight or nine years ago - so there are a lot of other characters and worlds and stories," Feige told Total Film.

"So should this film work, should the audience come out for this one, there are definitely places we can take it and we have ideas of where we'd like to go with it, but really all the energy goes into the first movie first."

With the possibility of more films comes the increased chance of more cameos. Feige confirmed to Total Film the infamous Thanos will appear in the upcoming Marvel film.

"Guardians of the Galaxy" will be released to theaters on Aug. 1.