K-9 is Marvin the Martian's pet alien dog and a recurring antagonist in the Looney Tunes franchise.
In the episode, Haredevil Hare, he was voiced the late Mel Blanc.
In Duck Dodgers, he was voiced by Frank Welker. In The Looney Tunes Show, K-9 usually has no voice actor, meaning that he does not speak. However, he does speak while singing in the Laser Beam song. He was voiced by Damon Jones in the Laser Beam song.
When Marvin the Martian appears as the main antagonist of some Looney Tunes episodes, K-9 is the secondary antagonist.
In the 2011 Looney Tunes TV series, The Looney Tunes Show, K-9 appears as a minor character in the series. He does not appear in episodes, he only appears in songs in a few episode such as I'm a Martian, Laser Beam and Christmas Rules.
K-9 is a lime green martian dog with a red nose, green ears, and black eyes.
Just like his owner, Marvin, K-9 wears a green martian helmet, a green skirt and white and red shoes.
In K-9's first appearance, Haredevil Hare, he seems to be unintelligent and gullible. He often snorts while he laughs. In K-9 Kaddy, K-9 was shown to be ticklish when two alien gophers tickle his belly and chin with feathers.