List of Transformers Animated Episodes - Season 1: 2007-2008

A small repair crew, consisting of team leader Optimus Prime, hotshot Bumblebee, lumbering Bulkhead, ninja loner Prowl, and grumpy Cybertronian War veteran and medic Ratchet, find the Allspark among meteors when clearing a space bridge in an asteroid field. The crew is attacked by Decepticons including Megatron and Starscream, and are refused assistance from Cybertron. Starscream betrays Megatron; an explosion damages Megatron and he crashes on Earth along with the Autobot ship.

Fifty earth years later, in the city of Detroit, a nanotech demonstration by inventor Isaac Sumdac results in a giant monster, which local police and SWAT are unable to combat. The Autobots are accidentally woken up from their stasis nap. Taking on new vehicle forms, the Autobots battle and defeat the nanotech creature, and also meet Isaac's daughter Sari Sumdac, a spunky 8-year-old girl whose security key card is transformed by the Allspark into a transformable key capable of healing the Autobots' injuries. Prowl is badly injured and healed by this method. The Autobots become the city's "Cybernetic Superheroes", and put their skills to work helping people.

The Autobots continue to defend the city while making their home in the abandoned automobile plant Sari set them up in. Sari uses her key to accidentally revive Megatron's head, who promptly learns of Starscream's betrayal. Megatron controls a small "Pocket-Bot" to search for the AllSpark in the Autobot's base, but when he doesn't find it, he takes control of the machinery in the plant to kill the Autobots. The Autobots hold their own and emerge victorious, and ponder who could have controlled the "Pocket-Bot" in the first place.

After having his funding cut by Porter C. Powell after Cyrus "The Colossus" Rhodes goes berserk during a demonstration, Prometheus Black experiments with the fluid leaked by Bumblebee which grants him acid powers. Calling himself "Meltdown", he vows to eliminate Isaac Sumdac, but the Autobots prevent his plans.

Megatron reveals himself to Prof. Sumdac and tricks the inventor into thinking that he is an Autobot. He then helps Sumdac in reprogramming some robotic dinosaurs after Bulkhead accidentally destroys them at a robotic theme park. While Sumdac tries to rebuild them, Prowl teaches Bulkhead how to 'think and move'. Behind Sumdac's back, Megatron upgrades these Dinobots – Grimlock (a Tyrannosaurus), Snarl (a Triceratops) and Swoop (a Pteranodon) – to become his new attack drones. But during their rampage, both Ratchet and Bumblebee try to use an electromagnetic attack to disable them. However, Sari's key gets pulled into the mix, which gives the Dinobots a small semblance of "a spark". Megatron tricks them into attacking the Autobots because "Cars bad. Cars that turn into robots worse."; this forces the Cybertronian heroes to battle them. It is during this fight that Bulkhead proves to be exactly what the Autobots need to stop the Dinobots, his muscle more than a match for the Dinobots' muscle. Sumdac thinks it would be better to dismantle the Dinobots, and Prime agrees, but Prowl (who senses a life force inside them) and Bulkhead, without Prime's knowledge, take the Dinobots to an island in the middle of Lake Erie where they can exist peacefully.

Ratchet thinks back to the time when he served in the Cybertronian War as a field medic. During the fighting, he was sent to rescue an Intelligence agent named Arcee who was injured during the fighting. The intelligence codes she possesses could turn the war in the Decepticons' favor. For that reason, Megatron sends Lockdown to capture her, snagging Ratchet in the process. In order for the Decepticons not to receive the codes, Arcee tells Rachet to use his EMP generator to wipe out the codes. He reluctantly obeys and the aftermath is Acree losing her memory and Lockdown gaining Rachet's EMP generator. Back in the present, Lockdown has resurfaced and uses Ratchet's EMP generator to capture Optimus Prime. Recruited by Blitzwing and Lugnut to locate the Autobots who destroyed Megatron, Lockdown is revealed to be just a bounty hunter who doesn't care about the Decepticons' cause and just does it for the 'upgrades' he can get. Ratchet eventually defeats him, reclaims his EMP generator and saves Prime, and opens up about his experiences to his leader.

To obtain Destronium to help rebuild his body, Megatron bails a fleet-footed thief named Nino Sexton out of jail. He provides Sexton with Isaac Sumdac's experimental super-speed suit, and Sexton takes the name "Nanosec". Since the Destronium is highly unstable it needs to be transported quickly from the research lab to Megatron directly. Meanwhile, to catch up to the villain, Bumblebee experiments with some new rocket boosters, but they do more harm than good. Eventually, the Autobots exploit Nanosec's weakness (rapidly accelerated aging) and defeat him, and through teamwork, get rid of the exploding Destronium.

It's Halloween and Sari introduces the Autobots to Earth's costume-and-candy traditions. However, the entire affair brings up bad memories for Optimus, who is haunted by the ghosts of his past, specifically when he and his fellow bots, the cocky and arrogant Sentinel Prime and power-mimicking Elita-1 were looking for a crashed Decepticon ship loaded with energon cubes. When Sari takes Bumblebee and Bulkhead trick or treating, the spider-like Decepticon Blackarachnia (formerly Elita-1) shows up and targets Sari's key. She wants the key to get rid of her organic half that she got when she was on an organic planet infested with giant spiders. The spider's venom somehow mutated her Cybertronian systems, making her "a freak". After seeing how Sari's key can heal Autobots, she wants to use it to purge her organic half. However, her body can't survive without her organic half now and as a result of using the key, she nearly kills off all organic matter in the entire city (which includes herself and Sari). Optimus gets the key away from her and Blackarachnia escapes, alone once again.

Megatron creates Soundwave, a toy robot for Isaac to give to Sari for her birthday. Bulkhead is the only one who finds the toy to be a bad thing and discovers the toy is evil. Unknown to Sari, the more she uses her key on Soundwave, the more he will evolve into a bigger robot, which Megatron intends to use as a new body. However, after using the key many times, Soundwave becomes self-aware and assembles all the robots in Detroit to create an army. When the Autobots catch wind of Soundwave's plan, they try to stop him. Most of the Autobots get overwhelmed, but Bulkhead confronts Soundwave in the sewers. Soundwave tries to convince Bulkhead to his logic. Bulkhead tricks Soundwave and smashes him to pieces, but Soundwave survives as a cassette player.

Megatron's two deadliest warriors, the three-faced Triple changer Blitzwing and the strong, obsessively loyal Lugnut arrive on Earth looking for their leader Megatron, and tear up the city of Detroit. Optimus Prime and the Autobots battle the highly destructive Decepticons, only to get beaten back by their seemingly endless arsenal of weapons. Megatron, seeing that Lugnut is the most loyal, manages to make contact Lugnut and orders him to obtain Sari's key. With the key they can locate the Allspark, and with that Megatron will be able to return to power. Optimus decides to use Sari's key to repair their ship so that they can get off the planet and lure the Decepticons away from them. But Sari doesn't want them to go and stubbornly refuses to help them, even to the point of sabotaging their ship. However, the Allspark reveals that if Megatron gets the Allspark, he will destroy everyone and everything in the universe. While Optimus and the Autobots battle Blitzwing and Lugnut, Ratchet and Sari reactive their ship's weapons system and blast the pair into scrap. Starscream suddenly appears and promises to save and repair them, but demands them to serve him only.

Sari is abducted by the Dinobots. Prowl and Bulkhead go to Dinobto Island to investigate, followed by Capt. Fanzone. The trio are attacked by the Dinobots, and discover they all have acid burns on their bodies. Worse, it is the work of Prometheus Black (AKA the acid-shooting Meltdown) who has forced the Dinobots to become his watchdogs, and wants to use Sari as part of his experiments to create a transforming human. His previous experiments having failed, Meltdown thinks that a still-growing human, as opposed to an adult, will have better results, and chooses Sari because he hates Sumdac. Bulkhead is heavily injured by Meltdown, and only Sari's key can save his life. Prowl and Fanzone team up to release the girl, but they have first to fight Meltdown's mutant freaks. They take out Meltdown by wrapping him in a non-corrosive containment suit and, after the Dinobots take out Meltdown's mutants, return to the city, leaving the Dinobots on their island.

Sumdac employee Henry Masterson is fired for creating weapons of war. To take revenge on Sumdac, Masterson uses his exo-suit invention to become "The Headmaster". He eventually succeeds in taking over Bulkhead's body, and fights the Autobots using it and weapons built into the Headmaster unit. He also causes the city's generator-core to overload, threatening to destroy the city. By the time the Autobots defeat Headmaster and knock the Headmaster unit off Bulkhead, the overload is at the point where the only way to stop it is to manually push the containment-grid back into position. However, nobody can survive the conditions inside the core, so it's essentially a suicide mission. At first, Optimus plans to do it himself, but Bulkhead has the idea of creating a new robot to do it. The Autobots create a patchwork robot in time, and Sari animates it with her key. The robot succeeds, and its melted, damaged, inanimate remains are put on display.

Prowl is frustrated by humans plowing snow and the fact that neither Bumblebee nor Sari seem to care. Optimus Prime discovers a non- sentient Cybertronian energy signal and Sari, Prowl, and Bumblebee set off to investigate. Sari attempts to teach Bumblebee the fine rustic art of camping, but he is not the least interested in roughing it. Their semi-peaceful vacation is soon disrupted when they have a run-in with parasitic Space Barnacles, that have apparently taken over the Cybertronian body of their thought-to-have-been deceased enemy Megatron, and end up taking over Prowl and Bumblebee. Sari uses hot water to destroy the space barnacles. Her Autobot friends are rescued, but Prof. Sumdac finds the body and takes it back to his lab to rebuild it.

Absent: Ratchet, Bulkhead, Capt. Fanzone

When Starscream, Blitzwing, and Lugnut begin their attack upon Earth, Optimus Prime demands that Sari hand over her key to the Autobots. She refuses and Rachet uses his magnets to forcefully take it from her. Upset, Sari runs away and is captured by Blackarachnia. Optimus begins to doubt his leadership while Megatron begins his next stage to have his body rebuilt. Lugnut and Blitzwing steal the key from the Autobots. Starscream, when scanning Lugnut, learns at last that Megatron is really alive. After thinking a little, he decides to join up with his former leader until the next good opportunity to get rid of Megatron presents itself. Starscream arrives at Sumdac's lab, where Megatron's head is kept, and tries to convince him of his loyalty, not suspecting that Megatron already knows about his treachery. Later, Optimus watches in horror as Megatron rises to the sky, his body having been fully rebuilt by Isaac Sumdac and the Allspark key.

With his new body, Megatron successfully defeats Optimus, Prowl, and Bulkhead, and kills Starscream as punishment for betraying him. After tricking Blackarachnia, Sari joins up with Ratchet and they pick up Prof. Sumdac and the other Autobots at Sumdac Tower, with Megatron, Lugnut, and Blitzwing in hot pursuit. Crashing on Dinobot Island, the factions battle each other, and Optimus disperses the Allspark using Sari's key, seemingly killing Megatron. With the AllSpark out of commission, Sari's key becomes the most powerful Cybertronian artifact in existence. Megatron survives, with Prof. Sumdac as his prisoner.