After months of speculation, Guardians of the Galaxy director James Gunn confirmed last month that Nathan Fillion does have a cameo appearance in Marvel's Phase Two adventure, but denied the rumor that he was playing Richard Rider, a.k.a. Nova. Another unconfirmed report from later that month revealed that the actor was actually voicing the role of Cosmo, the psychic Russian cosmonaut dog who serves as the security chief of Knowehere.

Today, Stitch Kingdom has gotten a hold of the full Guardians of the Galaxy cast list, which reveals who Nathan Fillion is playing, along with Marvel legend Stan Lee's cameo and a surprise voice role by musician/filmmaker Rob Zombie. Take a look at the character details below.

"Stan Lee will have his customary cameo, this time as the 'Xandarian Ladies' Man;' browncoat favorite Nathan Fillion will be dolled up as 'Monstrous Inmate;' musician Rob Zombie lends his voice as the 'Ravager Navigator Voice;' and writer/director James Gunn himself will appear in the film as one of the 'Maskless Sakaaran.' Also appearing in the film, though not a cameo, is actor Fred the dog who assumes the role of Cosmo."

In addition, Stitch Kingdom also reports that Howard the Duck will be referenced somewhere in the movie.

"Marvel legend Howard the Duck is somewhere to be found in the film. This inference comes from a line in the end titles that credits co-creators Steve Gerber and Val Mayerik. Whether it's just a film/comic Peter Quill was familiar with before he was abducted from Earth or we're about to have a new entry in the Marvel Cinematic Universe is just about anyone's guess."

Are you excited to see Nathan Fillion's cameo? Chime in with your thoughts below. How do you think Howard the Duck fits into the story?