Tails, Knuckles and Amy are playing cards in Tails' House when Sonic bursts in excitedly, showing them what he found at the flea market: Tomatopotamus 2, a video game they loved when they were younger. This causes much rejoicing (and leads to brief complaints about how the series didn't work in 3D). When Amy wonders why they stopped playing it, Tails explains that there was a mass recall of the cartridges in order to melt them down because their microchips were made of Sparcium, a rare alloy more valuable than the cartridges themselves. The four launch a game in competitive mode. Sonic gloats that, by virtue of being undefeated thus far, he's the master of the game, even saying he'll buy chili dogs for everyone if he loses. Meanwhile, Eggman is working on his newest robot created to kill Sonic: the eponymous FiendBot. He's big, strong, covered in missile launchers, and being programmed with data and recordings of Sonic in action from previous episodes to make him able to predict Sonic's actions.
Back at Tails' House, the fox is eliminated from play, quickly followed by Amy (despite her attempting to say that girls are good at games, too). The duel between Sonic and Knuckles lasts 14 hours and 27 levels, ending with Knuckles' victory (but only because the last level was an aquatic level, triggering Sonic's fear of water). As Knuckles gloats like hell, Sonic angrily goes to buy the team chili dogs as promised. Meanwhile, Eggman finishes loading FiendBot with data and decides it's time to take him to the Village Center for a test drive.
At Meh Burger, Sonic is buying the chili dogs when he gets attacked by Eggman and FiendBot, and sure enough, FiendBot's absolute knowledge and predictions of Sonic's actions works well, giving the hedgehog some real trouble as his robotic foe adapts to his every move. However, Eggman programmed his creation a bit too well. Eventually, FiendBot sees Sonic put the fight aside and endanger himself to rescue civilians; he starts analyzing this new data and comes to a conclusion: "Sonic not enemy. Sonic... friend?" Believing he's only kidding, Eggman nervously tries to get him to attack Sonic again, but a missile salvo from his now-former minion makes him run away. A bit confused by what happened, Sonic thanks him for not killing him, then tries to go back to Tails' House... but FiendBot starts to follow him like a lost puppy (complete with the eyes), and he has to tell him not to, because he knows his friends won't be fans of the idea of an Eggman robot befriending him.
Sonic returns to Tails' House and hands over the chili dogs as Knuckles continues to bask in his victory when there's a sudden loud thudding outside. Knowing all too well what that means, Sonic attempts to keep them from going outside, but soon, they see FiendBot and immediately try to attack; stopping them, Sonic is forced to tell them what happened, and as he figured, they're skeptical that a robot of Eggman covered in missile launchers and named FiendBot has pulled a Heel–Face Turn. Sonic, while admitting the name is a bit harsh and suggesting to re-baptize him FriendBot, comes to the robot's defense, saying that he could have easily destroyed him at any time and asking them to give him a chance, which they begrudgingly do. Meanwhile, at Eggman's base, the scientist, furious that FiendBot's sentience was ultimately detrimental for him, makes a second attempt— this time with a massive cannon programmed with data of Sonic like the robot that was formerly his, but without the sentience.
Cut to a montage of Team Sonic and their new companion enjoying volleyball, playing video games, and dancing... and each time, FriendBot's size and strength cause problems. Because of this, he doesn't get much love from Tails, Knuckles and Amy. They later go to Meh Burger and get attacked by Eggman with a massive army of basic bots, Obliterator Bot, and Mega Bot. As the battle begins, FriendBot makes short work of Mega Bot and Obliterator Bot, impressing Tails and Amy, but angering Knuckles, who sees his place as the strong guy of the team jeopardized. Seeing his opportunity, Eggman brings out the energy cannon, which begins to chase Sonic. The Blue Blur is quickly trapped and at the non-existent mercy of the killing machine, but just as it fires, FriendBot takes the shot and collapses, his systems shutting down. The selfless act finally convinces Tails, Knuckles, and Amy of FriendBot's loyalty, with Knuckles outright admitting that Sonic was right about him since the beginning. After that, the cannon doesn't last long against the wrath of our heroes, and Eggman is sent packing again.
At Tails' House, the rest of the team waits anxiously inside as Tails tries to repair FriendBot outside. The fox returns with bad news: FriendBot's AI processor is destroyed. The good news is that he can replace it, but more bad news: Eggman made the old processor out of Sparcium, meaning that in order to create a new one, the gang will have to sacrifice their Tomatopotamus 2 cartridge. Knuckles is at first reluctant to give up the proof of his triumph over Sonic, but quickly concedes; the cartridge is destroyed, the repair succeeds, and FriendBot is restored. While the team is happy to see their friend saved, Sonic says that he can't live with them because he's too big to fit in any of their houses. But a solution is found: FriendBot will live in the Valley of the Cubots. He'll have all the space he needs, the Cubots will have a protector in case Eggman comes back for them, and it's close enough that the team can regularly visit him or he can come to their help (he has his own Communicator now). The episode ends on an aww-worthy group hug (and FriendBot promising to remember Knuckles is the Tomatopotamus champion upon his prompting).
This episode provides examples of:
- Biting-the-Hand Humor: The criticisms Team Sonic give regarding the Tomatopotamus franchise are clearly based on those levied at the Sonic franchise over the years, including the opinion that the games play worse in 3D.Sonic: They never should've changed the color of Tomatopotamus's legs.
- Disney Death: Friendbot.
- According to Word of God, there were arguments on whether making it this trope or Killed Off for Real. Eventually, Word of God remembered this was a kids' show.
- Expy: Friendbot is one of the Iron Giant.
- Gentle Giant: Friendbot.
- Grew Beyond Their Programming: Fiendbot is Eggman's most mentally advanced robot designed with the ability to learn and think critically, this allows him to turn against Eggman due to realizing Sonic is a hero. To avoid this a second time, his next attempt is explicitly non-sentient.
- Heroic Sacrifice / Taking the Bullet: Friendbot does it for Sonic towards the end.
- Literal-Minded: Friendbot has a moment.Sonic: He could have destroyed me, but he didn't!Knuckles: Big deal! I could destroy you all the time!Friendbot: "Destroy"?! Potential threat to Sonic detected! (aims at Knuckles)
- Names to Run Away from Really Fast: Fiendbot. Lampshaded by Tails:Tails: HIS NAME IS FIENDBOT, FOR CRYING OUT LOUD!!
- Puppy-Dog Eyes: Fiendbot (he hasn't been rebaptized yet) does this at one moment. It's surprisingly cute.
- There's even a small, robotic purr!
- Roaring Rampage of Revenge: After Friendbot's Heroic Sacrifice, Knuckles and Amy completely annihilate the cannon.
- Sixth Ranger: Friendbot.
- Unsportsmanlike Gloating: Knuckles indulges into this after beating Sonic at the game. A bit of Laser-Guided Karma, eh, Sonic?
- Whole-Plot Reference: Word of God itself admits the episode was heavily based on The Iron Giant.
