Cosmo was a specimen from a U.S.S.R. space program and was brought to Taneleer Tivan's museum as a part of his obsession with collecting. When the Guardians of the Galaxy brought the Orb to Tivan, Rocket and Cosmo growled at each other as Carina told them about Tivan's collection.
When Carina unleashed the Orb's power, destroying much of the museum, Cosmo managed to survive the catastrophe and escaped but didn't leave the museum. Shortly afterwards, while Tivan, who also managed to survive, sat in the ruins of his museum, Cosmo returned to lick his face, as Howard the Duck commented that it was gross.
- Collector - Master
- In the comics, Cosmo was a test animal of the Soviet Space program. He was launched into Earth's orbit as part of an experiment in the 1960s but drifted off into space. He later arrived on Knowhere and became mutated, gaining telepathic and telekinetic abilities. The very uneasy relationship Cosmo has with Rocket Raccoon is referenced in the film when they growl at each other as the Guardians enter the museum.
- Given that Soviet Union dissolved in 1991 and the events of the film occur in 2014, Cosmo was likely at least 23 years old at the time (or perhaps considerably older, as most Soviet spaceflights with dogs took place in the 1950's and 60's). Considering that this is far longer than the average lifespan of most dogs, it is possible Tivan may have somehow slowed his aging.