Woodpecker from Mars (1956)

Woody Woodpecker is a guest at a television show and walks off with a space helmet and a space gun as souvenirs. He pretends to be a man from Mars, and is believed to the extent that he is caught and sent to an atomic laboratory for testing, which convinces the scientists he does belong on Mars. They send him to Mars on a rocket-ship and, once there, the Martians are convinced he is a crazy alien from Earth, and start testing him in their laboratories.