In a dark room, a scientist, Ben, secretly tells someone that tomorrow, the Feds (FBI) will be coming to shut down his department. The person he is talking to reveals himself to be a talking guinea pig named Darwin (Sam Rockwell). Ben tells them the only chance they have to avoid shutdown is to prove themselves.
Ben activates a hologram and shows him information on Leonard Saber (Bill Nighy), a former weapons dealer and current home electronics mogul. They believe that Saber has designed a new microchip (Project Clusterstorm) with military application and have evidence that he may have already sold some to the Middle East. The mission is to infiltrate Saber’s house and look for evidence on the new chip.
Cut to Saber’s house, it’s the evening and he seems to be having a party with many guests. Darwin is outside the house and checks on his teammates. Speckles, a star-nosed mole and communications/hacking specialist, directs the missions and the other agents from a hole in the ground.
Two other guinea pig agents, Blaster (Tracey Morgan) and Juarez are on their way as well, using scuba equipment and swimming towards Sabers house.
Darwin is having first mission jitters but gets over it.
Blaster gets out of the water and turns around to see Juarez get out of the water as well, but in seductive slow-mo fashion (reminiscent of that James Bond scene).
To get closer to the house, Darwin climbs into the wheels of one of the approaching cars and is able to get in, but with the side effect of being a little disoriented/dizzy.
Mooch, a housefly and the team’s surveillance specialist flies in closer to monitor the guests. Darwin sneaks into the coat closet, and cuts through the vent. Outside, Juarez and Blaster use grappling hooks to get up to the roof.
Darwin gets into Saber’s study and searches for the computer.
Meanwhile, Saber is giving a presentation to his employees about his new microchip, which will allow all Saber brand electronics to communicate with one another, allowing for importing preferences and information (I.e., coffee maker telling fridge to add coffee to the shopping list).
Back in Saber’s study, Darwin is hacking into his computer, jumping on the keyboard to hit the keys (he’s too small to type). Darwin finds the data and begins download. Mooch detects Saber walking towards his study and distracts him by flying up his nose. Darwin encounters a decryption program but Speckles uses a computer worm to get through. The download is taking too long but Darwin won’t abort the mission.
Saber notices that the fireplace is out and reactivates it, unfortunately for Darwin, it’s also his hiding spot. Darwin runs for it and is able to grab onto an escape rope set by Juarez and Blaster. On the roof, Darwin checks the download and its complete, they’ve got what they came for. Darwin gives the order to leave, but the entrance to Speckle’s hideout is discovered by a large guard dog.
The team head towards Speckles and parachute off the roof. Blaster aims towards the dog, hitting it on the head before getting caught in a bush. Juarez rescues blaster and the team run for it. They make it to the outside of the grounds but is stopped by a large exterminator van. A man in a full exterminator suit comes out and gases them.
Its turns out that exterminator is Ben, he was there to extract them. Mooch shows up as well. Everyone is celebrating the success of their first mission and Blaster suggests naming themselves “G-Force.”
The next day, Ben is preparing to present the team’s findings to his superiors while Speckles finishes up decrypting the files. While this is happening, the team has some down time. Blaster is playing on his DDR machine, while Juarez talks about love on Facebook. Darwin visits Juarez in her “apartment,” after hearing that she was interested in him, but it turns out she was saying that to make Blaster jealous.
Later that day, the higher ups show up to review the project and determine if it is worth further funding. The Agent responsible for deciding whether the project passes is Agent Kip Killian (Will Arnett). Ben shows him a few of the current projects, but Kip isn’t impressed. Ben then shows him a device that allows people to talk to animals and the G-force team introduce themselves. Kip isn’t happy that Ben went ahead and started a mission into Saber’s home without his permission, but is willing to hear him out.
Ben tells Speckles to show them what they found and Speckles loads the file, and it turns out to be the blue prints to an espresso machine. Darwin is caught by surprise because he specifically downloaded the Clusterstorm file, but it seems that he may have made a mistake.
Kip decides to shut down the project and send in people to collect the animals and shut the lab down. With the help of Marcie (Kelli Garner), the team escape the building via pneumatic transport tubes. Outside, they climb into a delivery truck and get inside a cage. The truck arrives at a pet store and introduced to the locals. The first one they meet is a psychotic little hamster named Bucky (Steve Buscemi), the other resident is a flatulent old guinea pig named Hurley (John Favreau).
They try to break out of the cage but do not succeed. Fortunately, Mooch had followed them and Darwin instructs him to find Ben and tell him where they are, and to warn him that there is only 29 hours left until project Clusterstorm is activated.
At FBI headquarters, Ben’s proposal to reinstate the program is shot down and he leaves with Marcie to come up with another plan. When asked about what to do about the missing team members, Ben says that they’re probably halfway back to the safe house by now.
Cut to the guinea pigs still trapped at the pet store. Blaster gets Hurly to let off a huge fart, which he lights with two pieces of stone, producing a huge fireball, but the glass is unaffected and Blaster is lightly singed. Darwin asks Hurley for ideas, and he says to act cute and be adopted. Darwin orders his team to act cute when a family comes in and a brother and sister adopt Juarez and Hurley, but the brother throws Hurley at the snake pit. Fortunately, Hurley lands on the outside of the cage and the snake knocks itself out trying to attack Hurley. The kid adopts Blaster instead.
At the little girl’s house, the girl dresses Juarez in a dress and paints her nails, much to her disapproval.
Back at the pet store, Speckles pretends to be dead so that he would be buried in the back yard, but the boss tells the guy to just toss him into a passing garbage truck. Darwin watches as the garbage truck close and crushes the bag Speckles was in.
Back with Ben and Marci, Ben uses a genetically engineered cockroach to sneak back into his old lab, which is now guarded by the FBI. The roach calls up other roaches and swarm the area. While the agents are grossed out and distracted, the lead roach makes off with the PDA containing the data Darwin had retrieved earlier.
Back at the pet store, Hurley notes he and Darwin both have the same birthmark and says that they might be brothers, much to Darwin’s horror.
Ben retries loading the data from Darwin’s PDA but the data is being guarded by a powerful computer virus.
At the pet store Darwin hears a noise and checks it out, it turns out that Bucky has a secret door in his little hut and has been using it to sneak out food at night. Darwin is angered that Bucky didn’t tell him about the exit, especially because it could have prevented Speckles from being killed in a garbage truck. Darwin prepares to leave and Hurley gives him an awkward, tearful goodbye hug. Hurley says that he’ll miss Darwin, but Bucky pushes him into the hole and now he has no choice but to follow Darwin.
Saber gets a call from an unseen Mr. Yanshu about project Clusterstorm. The project apparently involves tracking objects floating in space ( junk). This Mr. Yanshu is apparently an anonymous engineer working for Saber.
Mooch finally finds Ben and tells him where the team is. At the same time, the BI show up at the pet store looking for the guinea pigs. Darwin and Hurley are now on the outside and begin searching for Juarez and Blaster. Ben and Marci show up at the pet store looking for the guinea pigs but find out they’re gone, and that the feds are also looking for them.
Cut to Blaster being put in a remote controlled car and made to do stunts. Blaster is enjoying himself and when the kid controlling his car leaves to do his chores, Blaster grabs the controller and drives himself down the stairs to find Juarez. Outside, Juarez is stuck in a door house but breaks out, signaling Blaster to drive by and she jumps in.
Hurley and Darwin are still searching but end up in front of bakery. Hurley talks about cake and how it’s like his Holy Grail of foods, and Darwin spots the same espresso machine that he saw on t file earlier and goes in to investigate. Digging through the machine, he finds a military grade transmitter chip normally used in unmanned aerial vehicles, not household appliances. He tries to remove the chip and take it back for evidence but this causes the espresso machine to transform into a killing machine (kind of like Transformers), armed with spinning blades and some kind of plasma gun.
Darwin jumps onto the machine but gets knocked off. After a bit of dodging and running, Darwin lures the machine into the middle of the road and it gets run over. It seems evident that Saber has been weaponizing his entire line appliances. Darwin piles the dead machine onto a skateboard and pushes it back to base. Everyone gathers back at Ben’s lab, except for Speckles. Ben finally reveals that they are not in fact genetically engineered super animals, but just regular animals he rescued from pet stores, restaurants and cosmetic labs.
Meanwhile, the feds get a call about giant hamsters pushing a skateboard around and head off to investigate.
Back at the lab, Darwin has lost faith in himself, but Hurley notes that he’s got what it takes to be a leader (escaping the dogs, beating the espresso-terminator, and finding his way home). Darwin comes around and decides to finish the mission and bring Saber to justice.
Unfortunately, since their last lab was closed down by the FBI and their gear confiscated, it seems that they have no equipment for this mission. Fortunately, Ben reveals that he has been secretly working on a prototype transport vehicle and has spare equipment they can use. Just then, the FBI shows up and demand they turn over the guinea pigs.
Outside, the FBI are still banging on the door when there is a loud crash and the G-Force ball cycle goes flying through the window. This is followed by a long, loud, and partially 3-D car chase with the guinea pigs finally out-maneuvering the FBI and escaping.
Later that evening, the team arrive at Saber’s home. Inside, Saber and some of his staff are preparing to celebrate the impending launch of Project Clusterstorm. The count down timer reaches zero and suddenly, all the appliances around Saber’s house start to move and attack. Saber is clearly confused and seems to have no idea that project Clusterstorm would do this.
In the ventilation shafts, Darwin, Blaster and Juarez head down towards the main computer to disable Clusterstorm, and Hurley (who has tagged along) is instructed to stay put and watch their exit.
As the team descend and search for a way down to the central computer, Hurley decides to go exploring. Hurley ends up in the pantry and scrounges for food, until he spots a slice of cake in the microwave. Of course, cake being Hurley’s dream food, he climbs into the microwave and is trapped. The microwave transforms into a killing machine and stomps off, looking for victims (along with Hurley inside it as a hostage).
Down in the basement of the house, the team is getting close to the central computer but spot a trap, a trip wire connected to a bomb. They carefully avoid it but suddenly, the killer microwave with Hurley inside stomps in, trying to kill the guinea pigs. Darwin goes to save Hurley while Blaster holds back the machine so it won’t step into the trip wire. After a bit of struggling, Darwin is able to grab Hurley and toss him out, but Blaster’s cable snaps and the machine falls onto the wire. The bomb goes off, destroying the microwave and tossing Darwin far away. The team is now separated due to falling debris from the explosion. Darwin sets off the complete the mission while the others attempt to stop the other machines from killing everything in site.
Darwin finally reaches the main computer to find… Speckles! Darwin is relieved and thinks that Speckles has come to disable project Clusterstorm, but Speckles reveals that it was he who started the whole thing. Pretending to be an anonymous engineer, Speckles modified the designs of Saber’s home electronics, making them all capable of being killing machines. Not only that, once they are all activated, the machines will be able to generate a magnetic field strong enough to pull down space debris and bombard the earth. It turns out that Speckles once had a family, but they were all killed when his home was destroyed to make way for a new golf course. Speckle’s father told him that if he ever got a chance to take revenge on the humans, he should do it.
Darwin tries to stop Speckles, but he initiates the final part of his plan and the central computer transforms into a massive robot, combining with other household appliances to become bigger and deadlier (very much like Transformers). As the machine rises, Darwin is knocked off to a lower level and he spots Hurley. There is no way for him to get back up to Speckles, but Hurley decides to sacrifice himself to help Darwin. Hurley ties a rope to himself and jumps off the machine, and since Darwin is connected to the same rope on a pulley, he is shot upward towards the control deck.
At this point, the FBI show up to arrest Saber, but find out that he’s the victim of this. Things are going badly for the FBI as no one can stop the giant robot Speckles is controlling. Agent Killian is in a FBI communications van trying to coordinate an attack until Ben and Marci show up. They show them live video of Darwin trying to stop Speckles.
Darwin tries to plead with Speckles but he won’t hear it. The giant machine grabs the FBI van and starts to crush it. Darwin sees this and tells Speckles that he has a new family now, G-Force, Ben, and Marci are his new family, and he is about to destroy them. Finally realizing what he is doing (having one of those “what have I done?!?!” moments), Speckles tries to shut down the machine. Unfortunately, its on autopilot now and there is nothing he can do. At the last minute, Mooch shows up carrying the PDA containing the computer virus. Darwin plugs in the PDA and the machine’s computer system is fried, deactivating all Clusterstorm machines. As this happens, the machine Darwin and Speckles are in bursts into flames, explodes, and begins to collapse. As Darwin and Speckles fall, Darwin catches Speckles, and Juarez swings in with a parachute, carrying all the safety.
As everything calms down, it seems like everyone is ok, but Hurley is missing. Blaster finds Hurley under some rubble, but he’s not moving, still clutching his piece of cake. Darwin gives Hurley a tearful goodbye, and calling him brother, but Hurley’s noise twitches, smelling the piece of cake… he’s alive.
Some time later, the G-Force team is made official, and they’re all made into special agents, even Hurley, who gets a rookie badge. Speckles is made to atone for his actions by helping Saber’s company to remove all the Clusterstorm chips and Agent Killian has been moved to the Antarctic branch as punishment for getting into G-Forces way. All is well.
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