A friendly Galaxian who has seen the Guardians of the Galaxy film has provided us details about the role of a certain character from the Guardians comics. If you are avoiding all spoilers for the film, please don't read any further!
We are told by our source that Cosmo (the Russian space dog) does appear in the film as part of The Collector's collection. He is said to be "wearing the space suit, but doesn't have any dialogue." In the film, The Collector's cages are shattered and all of his collected species break free. This leaves room for Cosmo to appear in the sequel with a much larger role!
Cosmo could, however, have a speaking role in the post-credit scene of the film, which James Gunn said will go unseen until the wide release of the film on August 1st.