Marvin the Martian’s dog is named K-9.
K-9 is Marvin’s pet alien dog in the Looney Tunes universe. Like Marvin, he is associated with Mars and is usually depicted with green fur, a helmet, a skirt-like uniform, and four footwear-like slippers. His name is a pun on “canine,” the word for a dog.
K-9 first appeared alongside Marvin in “Haredevil Hare,” a 1948 Bugs Bunny short directed by Chuck Jones. In that debut, Marvin and K-9 are present as a pair of Martian antagonists, although neither character is named within the film. The dog’s identity and name became established through later appearances and reference material.
Readers sometimes confuse K-9 with generic robot-dog characters from other science-fiction series, or with dogs belonging to unrelated cartoon characters. K-9 is specifically Marvin’s pet, not Marvin’s assistant or another Martian villain. He has appeared in later television shows, films, games, and expanded Looney Tunes productions, though he is less prominent than Marvin himself.