In the comics, Cosmo is a telepathic Russian dog in the Marvel universe. He was created by Dan Abnett and Andy Lanning, and first appeared in Nova vol. 4 #7. Cosmo is the security chief of the space station Knowhere, and a member of the Guardians of the Galaxy.
Cosmo is part of the Collector's Museum, and he is first seen when he growls Rocket. In a post-credits scene, after the explosion caused by the Collector's slave, Carina, Cosmo appears licking Tivan's face, which seemed disgusting to Howard the Duck.
While not appearing in this film, Cosmo does show up in the credits, dancing to music.
Cosmo resides on Knowhere as its security chief when he encounters Drax the Destroyer, Rocket Raccoon, and Groot's stick form. He greets the group and escorts them until Rocket and Drax are captured by Knowhere's cords. Cosmo manages to escape with Groot's stick form to warn the Guardians that Knowhere had come alive.
Cosmo appears in the second installment of the series as a non-playable character in the game's Guardians of the Galaxy playset. He is the security chief of the space station Knowhere and guides the Guardians through gameplay.
Similar to his appearance in Guardians of the Galaxy, Cosmo can be found in the Collector's archives in the Guardians of the Galaxy - Mission: BREAKOUT! ride. He is portrayed as an animatronic kept in a tank within the queue.
At the end of the ride, he can be seen escaping his cell with the rest of the Guardians of the Galaxy. Strangely, instead of being a brown Labrador like in the film, Cosmo appears to be a Golden Retriever.
Cosmo's likeness appears on a gondola of the Disney Skyliner, being pet by Yondu.
- Cosmo's creation was inspired by the real-life Laika which was a dog sent to space by the Soviet Union in the 1950s.