During a particularly dangerous encounter with Eggman, Tails is injured. Sonic decides that being his sidekick is too dangerous for Tails and fires him for his own safety. Auditions are held for a new sidekick. Eggman applies for the job.
- Burnbot (First appearance)
- Doctor Eggman
- Fastidious the Beaver (First appearance)
- Mike the Ox (First appearance)
- Team Sonic
- Sonic the Hedgehog
- Amy Rose
- Miles "Tails" Prower
- Knuckles the Echidna
- Walrus Child (First appearance)
- Wild Cat (First appearance)
- Wolfie (First appearance)
- Sonic Boom World
- Dr. Eggman's Lair
- Seaside Island
- Mount Safety (First appearance)
- Sonic's Shack
- Tails' House
- Wrist controller
- Hoverboard (First appearance)
Within the crevasses of a canyon, Sonic the Hedgehog pursues his arch-nemesis Dr. Eggman, who is trying to escape in his Eggmobile. The pair enters a corkscrew-shaped mineshaft where Dr. Eggman summons Burnbot to destroy Sonic, but Sonic mocks the inconsistency of Burnbot's name, as its only weapons are a pair of pincer claws. Regardless, Sonic and Burnbot chase each other around the the mineshaft. Tails then arrives in the Tornado, where he contacts Sonic over his Communicator to set up their Speeding Swing Surprise. As Sonic and Burnbot are about to clash in the shaft, Tails flies in and helps Sonic by providing an Enerbeam for him to grasp, allowing Sonic to swing around and kick the robot into a wall. However, Burnbot gets up and clips the Tornado's wing, causing Tails to fall; Sonic pleads for Tails to eject, but faulty equipment leaves him stuck in the plane. Sonic rushes to help, but gets into another skirmish with Burnbot. With haste, he knocks a boulder onto it and exits the shaft, only to see Tails crash. As Sonic runs over to the wreckage, Eggman decides to retreat as well, taking Burnbot with him. Sonic finds Tails unconscious and in bad shape, but alive; as he carries him back home, Sonic vows to never put his friend in any more danger.
Back at Tails' House, Tails awakens to Sonic's joy. Tails is ready to get back in action, but Sonic instead tells him that he is entering early retirement from his job as sidekick. This explanation only leaves Tails confused, so Sonic tells him bluntly that he has been fired. Despite feeling guilty about his decision, Sonic begins advertising for his "sidekick try-outs," where all qualified candidates are welcome, so that Tails can stay in retirement. At Dr. Eggman's lair, Eggman, Orbot and Cubot learn about Sonic's try-outs. While Eggman finds this unbelievable (despite showing some interest in being Sonic's friend), it makes him hatch an evil scheme.
At Sonic's Shack, the sidekick try-outs are at full swing, with Sonic as the interviewer and several participants awaiting. The first participant shown is an eager Amy Rose, who attempts to impress Sonic by juggling and singing "When the Saints Go Marching In" but fails twice. The next candidate is Fastidious Beaver, who he admits that he is a coward. Finally, Knuckles the Echidna enters the try-outs, though he believes Sonic is qualified to be his sidekick instead.
At the end of the try-outs, a cloaked figure applies and Sonic is impressed by his answers to the questions. However, the figure then clumsily uncloaks himself and reveals himself to be Tails, who is attempting to reclaim his role. Sonic refuses, but Tails notes that the poster never excluded him from applying. Eggman then shows up to apply for the job too, but while Sonic is against it, Eggman uses the same argument as Tails. Despite his disapproval of the idea, Sonic begrudgingly lets them move on to the next round and additionally accepts the Fastidious Beaver as a third candidate and alternative.
To test his candidates, Sonic has them race on hoverboards to Mount Safety to capture a red flag there. While Eggman gives Fastidious an early start to shut him up, Tails and Eggman soon take the lead. Eggman then tries to use his board's weapons against Tails, but the latter manages to avoid them while accidentally knocking Fastidious out of the race. As Sonic watches on, Tails and Eggman move onto the next part of it and fly towards the flag in their Tornado and Eggmobile. As they fly towards the flag, Eggman reveals that his real reason for joining the try-outs was to get rid of both Tails and Sonic, and picks up Burnbot from the jungle.
Despite Tails' best efforts, Burnbot manages to clip the Tornado's wing again and he crashes in a frozen lake, now unable to leave the plane. However, Sonic comes to his aid and pulls him out just before the Tornado sinks. Then he apologizes to Tails by confessing to him that he fired him in order to protect him. Eggman and Burnbot then face the duo again, except this time the robot has been upgraded with fire weaponry, which is used to crack the ice around them. Sonic falls into the water, and since he cannot swim, Tails is forced to pull Sonic out. Sonic tries to get Tails to escape on his own when recovery proves to be too difficult, but Tails adamantly refuses, and both plummet underwater. Though Sonic resigns to his fate, Tails perseveres, and the duo manage to not only resurface, but go airborne. From there, Sonic lands a hard hit on Burnbot, causing it to break through the ice and sink. Sonic and Tails then fly back to solid ground while Eggman retreats, promising to return with a better robot.
As the sun sets, Sonic and Tails reconcile and Sonic re-hires Tails as his sidekick due to his earlier actions. Back at Sonic's Shack, Amy demands a callback when Knuckles passes by and notes that finding his own sidekick has been unsuccessful. Noticing an opportunity, Amy auditions for Knuckles on the spot, sparking his interest.
- Burnbot is introduced.
- Tails still has the Tornado which he and his team acquired in Sonic Boom: Rise of Lyric/Sonic Boom: Shattered Crystal.
- When Mike the Ox is seen in the line to Sonic's Shack, his attire, horns and ears are all colored grey.
- In the Brazilian dub of this episode, Eggman is referred to as "Robotnik". That was the name given to Eggman and all his incarnations in the western territories during the Sonic series' first years.
According to Bill Freiberger, early drafts of the episode included Sticks the Badger. However, since there was so much that needed to be done in this episode, it was decided to remove Sticks from it entirely rather than bothering themselves with the work in including her.
- This episode contains the first footage shown of the series back in February 2014.
- The beginning of "The Sidekick" was used as the pilot presentation for the Sonic Boom television series.
- Like the first episode of Sonic X, this episode showed Sonic's weakness that he cannot swim and is saved by his close friend (In this episode, Tails saved him while in Sonic X, he was saved by Christopher Thorndyke).
- The fourth wall is broken four times:
When Tails attempts to eject from his falling plane the first time, the lever breaks, after which Tails looks at the viewer in confusion.
- When the camera takes a close up of Eggman, it immediately tilts to the floor, Eggman focuses the camera back to him, remarking, "Lousy security camera!"
- When Knuckles tries to change Sonic's name to 'Knuckles Jr.", Sonic looks at the viewer with an annoyed look on his face.
- When Sonic announces to Tails that he has "Early Retirement", Tails says to the viewer, "Wait, what just happened?"
- When Eggman shows his application form for sidekick auditions, his picture is similar to one of his released concept art.
- Sticks did not appear in this episode, therefore making it the first episode where a main character does not appear, as well as the first episode where Sticks does not appear in.
- This is the only episode where the Tornado aircraft appears.
- The DVD set Sonic Boom: The Sidekick borrows this episode's title.
- The plot of this episode was adapted for Sonic Boom 01 - Le partenaire ideal.
- In Finland, this episode was first published in Ruutu.fi on April 5, 2016.
- The design for Fastidious Beaver's parking ticket would be used for the Event ticket in Sonic Dash 2: Sonic Boom.
- This episode, along with the "Can an Evil Genius Crash on Your Couch for a Few Days?", "Sole Power", "Chili Dog Day Afternoon" and "It Takes a Village to Defeat a Hedgehog", were the only ones during the first season of Sonic Boom to be released in their production order in the United States.
- Concept artwork for this episode appeared in Sonic Boom: Fire & Ice.