Gribble got to Mars around 1986 when he was about 9 or 10. The Martians had kidnapped his mom, and he wanted to save her but he got there too late and the Martians had killed his mother. He stayed on Mars for the next 20 years, inventing things and becoming one of the most hot men there, even getting on to playboy magazine.When a 9-year-old boy named Milo came along, Gribble helped Milo rescue his mom. Meanwhile, Gribble developed a romance with Ki, a Martian woman, and decided to remain on Mars with her. Ki and Gribble are last seen on Mars teaching the Martians the old values of Mars when Martians raised their families similar to Earth families.
Role in the film
Milo hears Gribble telling him to escape via chute while avoiding a pair of Martians preparing to kill him to which he uses his robotic assistant Two-Cat to rescue him just as Milo encounters him playing a space flight simulator video game. When Milo encounters him, he introduces himself to Milo who is trying to find his mother. Gribble gives Milo a belt to which he calls the "Gribblemeister 3000" to help him withstand low gravity. Gribble then tells Milo to look at the footage of how he escaped from the Martians. Looking at the footage, Gribble gives Milo a translator to understand what the Martians are saying to which it is found out that Martians trying to catch Milo are arguing during the chase, leaving them distracted. Gribble then takes Milo to another room for Milo himself where he introduces the creature inside the room as Wingnut just as Gribble and Milo become friends where he explains to Milo that he likes playing video games all day and watching TV all night. The conversation is interrupted when Milo sees footage of his mother preparing to be terminated by the Martians. Telling Gribble about this tragic plan, he explains to him about that Martians are born popping out of fragile ground every 25 years and the Martians have bad treatment to their own babies and all the Martians taking control of the chamber are females followed by the Martians building Nanny-bots to raise them.
Gribble then shows footage of Milo and his mother's moments at Earth before Milo's mother was abducted just as Gribble explains that the hobbies the Martians do are order and discipline to which Milo tells Gribble about what the Martians will do to his mother. He explains to Milo that whenever the Martians abduct a human mother with a memory extraction machine, it takes out the discipline of her and puts it into Nanny-bots and all the memories from a mother are extracted and put into each Nanny-bot during sunrise. This causes Milo to be upset about this and causes him to make a plan to save her to which Gribble refuses just as he gives him a Martian wristwatch which shows the bars that give out the countdown to sunrise, explaining that Milo has less then seven hours left before sunrise to save his mother. Gribble then devises a plan to disguise Milo as a Martian to avoid getting spotted by them.
During Milo's plan to get inside the Citadel, Gribble loses contact with Milo and ends up getting captured by the Martians. With help from Two-Cat, Milo arrives and saves Gribble from being killed by the Supervisor just as he and Milo escape the Martians' chamber via blaster. Milo and Gribble end up encountering Wingnut and a tribe of male Martians to which the SISS soldiers arrive and start shooting at the two as well as frightening away the other Martians. As the two end up in the translucent water area, Milo shows a Gribble a t-shirt of him and his mother. During this tragic flashback, he explains that he was a good boy before his mother was abducted by Martians and when Gribble plans to rescue his mother from Outer Space in Mars, Gribble attempted to stop the Martians from taking his mother's memories, but to his empty protests, the sun rose and took her memories as Gribble lost his mother with her memories transferred to the Nanny-bots.
With help from Milo, Gribble then plans to team up with him to get Milo's mother back just as Ki and Two-Cat also arrive to help. During the plan to find his mother, Gribble, Ki, and Two-Cat arrive at the rocket ship on the silo while Milo hurries to his mother in worry. Gribble and Milo plan to rescue Milo's mother while the Supervisor sounds the alarm to go after the two passing through the airlock. Gribble then sacrifices himself to take care of the Martian soldiers, causing Ki to shout her name an activate the launch system that unleashes the rocket on the silo.
When Milo's mother is saved from a dangerous demise, Gribble gives her a spare helmet to give her oxygen while the Supervisor prepares to stop Milo, his mother, and Gribble to which Ki intervenes with this true meaning of family; the Supervisor is arrested for her lies and betrayal to the Martians. As the Martians celebrate, Gribble, Ki, and Two-Cat rejoice with Milo just as he, Ki, and Two-Cat leave for Mars. During the credits, Gribble works in conjunction with Ki, causing evidence of life spotted on Mars to be shown on NASA.
- At one point when Milo first meets Gribble, he mimics the iconic Darth Vader breathing from the Star Wars franchise.
- Gribble also makes certain cultural references in many scenes such as Dungeons & Dragons, Top Gun, the discontinued Smurf Berry Crunch cereal, He-Man, and many more.