K-9 is Marvin the Martian's pet alien dog.
K-9 premiered in the short Haredevil Hare where he and his his owner Marvin tried to thwart Bugs Bunny, who had stumbled on the pair's plans to destroy the Earth. He is given his first speaking role in this short, seeming quite unintelligent and gullible. This changes in later shorts where K-9 carries an air of superiority over his owner. In K-9 Kaddy K-9 proves to be ticklish when two alien gophers tickle his belly and chin with feathers.