Jerry first encounters Peep when he is laughing at Tom, then he sees a Martian girl pointing a gun at him. They become very confused at what the other one is, but seem to like each other. Then three other Martians join her and it is revealed her name is Peep. The other Martians mistake Jerry for The Great Gloop, a mysterious figure from their ancient scrolls, but Peep is sceptical. They decide to bring Jerry to their king, but on the way, Jerry and Peep are abducted by a Pootsnarfle. The other Martians make it drop them, and when they fall, Jerry catches Peep in his arms, and she kisses him for saving her.
The Martians take Jerry to their city Toledo, and another sign of Peep's love for Jerry is shown when other Martians flirt with him and Peep keeps him away. The Martians show him to their king, King Thingg, who also mistakes Jerry for The Great Gloop. A banquet is held in celebration, and Peep and Jerry dine together. Peep introduces Jerry to some Martian foods that he finds quite revolting, but he enjoys some Martian cheese. When Tom unintentionally destroys the city and the Martians sentenc him to be dumped in a lava pit, Peep is unsure, and when the Martians find out that Jerry is not The Great Gloop, but an Earthling, he is sentenced to lave too, but Peep steals a jetpack and gets both of them to safety. She tells them their planet is in danger from her people, and the three of them steal a flying saucer from the other Martians, and head for Earth, but unfortunately, Peep is knocked out, and they drift into an asteroid field. They wake Peep up and she freaks out that they are in an asteroid field, and steers the saucer out. Then the engine runs out, and they become stuck, while the other Martians overtake them.
While the Martians attack Earth, Peep repairs the engine, and the three heroes counter attack the Martians. The humans freak out when they see Peep is one of them, but she uses a special ray gun to reintegrate the humans who were disintegrated, and they realize she is on their side.
Then the Invince-o-Tron attacks with its vacuum and Tom, Jerry and Peep head back to their saucer to stop it. When it is destroyed, Peep does not give up an tries to get to its general circuits, however she is discovered and captured. Jerry steals Spike's bone and throws it into the Invince-o-Tron's head, making Spike attack the Invince-o-Tron. He rescues Peep, and together they free the people whom the Invince-o-Tron sucked up with its vacuum.
Tom, Jerry and Peep are regarded as heroes and make the front page. The next day, Tom and Jerry are rewarded, but Peep is absent. The Invince-o-Tron returns, being controlled by Spike, and Peep zooms in to help. She rescues Jerry, while leaving Tom behind, and she kisses Jerry.