Marvin Martian (or Marvin the Martian) is a fictional character appearing in the Looney Tunes cartoons.
Marvin wears a parody of a Roman soldier's uniform (a reference to Mars being the Roman god of war) with old-fashioned basketball shoes. His head is a black sphere with only eyes for features. He speaks with a restrained, uptight voice, courtesy of Mel Blanc. He hails from the planet Mars, but is often found elsewhere. He is often accompanied by his dog, "K-9," and sometimes by other creatures (one gag being freeze-dried Martians that become full-size on addition of drops of water).
Marvin has tried to destroy the Earth (it obstructs his view of Venus) with the "Illudium Q-36 explosive space modulator", only to be foiled by Bugs Bunny. He has battled for space territory with Daffy Duck, a.k.a. Duck Dodgers of the 24½ Century.
Animation director Chuck Jones was inspired by the idea when he noted that while Bugs' major enemy, Yosemite Sam was loud and violent, he was obviously no threat. So, he decided to create the opposite type of character who was quiet and soft-spoken, but in his actions was incredibly destructive and legitimately dangerous.
Marvin was never named in the original shorts, but decades later when the character attracted merchandizing interest he obviously needed a name, so the current one was selected.
