Rodimus Prime is a reformatted version of the Autobot Hot Rod.
Hot Rod is a headstrong young Autobot that transforms into a futuristic sports car (best guess is something based off of a Lamborghini Countach). His love for action is both a blessing and a curse, as it makes him useful on the field, but often gets him into trouble. Hot Rod has a special relationship with Daniel Witwicky, serving as an older brother model of sorts. As well as his standard blaster, Hot Rod has been known to shoot plasma blasts from his arms, and also has used a retractable saw blade to fend off enemies. He is the Chosen One, and is responsible for the defeat of Unicron using the Autobot Matrix of Leadership.
As Rodimus, Hot Rod is now reformatted into a taller, more imposing figure with different color distribution. His sportscar alternate form has now changed to reflect his new status as leader, much like Optimus Prime, and he can now transform into a "cabover Firebird" of sorts, keeping the same nose of his former car, but adding a large trailer to the back. Rodimus is still Hot Rod at heart, and this means that he can still be somewhat hot-headed. He also bears the burden of partially contributing to Optimus Prime's death, and this combined with simple worrying that he will never live up to his former commander leads him to constantly second-guess himself. It should be noted that Rodimus becomes Hot Rod again if he passes the Matrix on.
After the return of Optimus Prime, Rodimus relinquishes the Matrix, but there are several instances where he takes it back for a short time. At the end of Generation 2 he is reformatted by the ghost of Alpha Trion so that he no longer needs the Matrix to be his Rodimus version. It is also at this time that Cybertron is destroyed and he joins the Headmasters, a group of Autobots charged with finding a new homeworld. He is also thrust back into the position of leadership with the second passing of Optimus.
IDW Publishing Continuity
During the Autocracy storyline, Hotrod is first an obscured character who fires at Orion Pax (a younger Optimus Prime) and his squad of autobots. When given a mission to hunt Hot Rod down and kill him by orders of Zeta Prime, the Autobots comply, and follow Hot Rod's trail back to an ancient city called Acroplex, a district in Nyon, a slum of Cybertron. Hot ROd leads teh squad down a goose chase which ends once he shows them how the people of Nyon are living, oppressed by the Autocracy. At this moment, Nyon is attacked by Zeta Prime and his Omega Destroyers. Buying Hot od some time to get his people out of the city, The autobots fail to even destroy one of the Omegas, much less scratch it. In a last ditch effort, Hot Rod reveals he has planted numerous phase chargers beneath the city and detonates the entire city, so Zeta Prime is not able to harvest the sparks of those he wreaked havoc upon.
Much later, when Autobots and decepticons join forces to combat the autocracy, he joins the fight along with them. When Decepticons betray the Autobots, he follows them into hiding. When captured, the Deceptions attempt to recruit the young machine, but to no avail. He saves Optimus' life during his battle with Megatron, and he is last seen conversing with Optimus Prime about being a leader, foreshadowing his role as future Prime and carrier of the Matrix of Leadership.
Long ago, Hot Rod was in charge of a group of Autobots -which included Gizmo, Backbeat, Dealer, and Download- on Ki-Aleta whose job was the secure the magnificence - a map of everything in the universe - before the Decepticons got it. They had devised a plan to distract the omega guardians who guarded the omega bunker where the magnificence was contained. As they were about to secure the magnificence, the holo-matter projects being used to distract the omega guardians malfunctioned and the guardians discovered them. Most of them were killed and Dealer contacted Hot Rod telling him he was under fire and Hot Rod felt guilty he could do nothing to help him as he had orders that if the mission were to be compromised, that he should take the magnificence and use a back-door installed by a drone and secure it in a location known only to himself.
Much later, Hot Rod would attempt to break into the Decepticon prison, known as Styx, knowing that Dealer was being held captive there and he felt that he could still find some redemption in getting him out. He uses a virus to create false alarms throughout the base and also uses a hologram to disguise himself as he sneaks around the base. He eventually comes to the Z-Lateral cell block where he finds Dealer badly damaged but alive. He rescues him and then commandeers a ship and escapes with him. He tries to apologize to Dealer for what he did but Dealer tells him he understands why he did what he did and is grateful that he came to rescue him.
See Hot Shot
Rodimus was one of the main characters in the second entry to the Unicron trilogy He first appeared in the episode 11 "The Legend of Rodimus". He is Hot Shot's inspiration and hero. Rodimus was a military commander. After growing tired of the never ending war on Cybertron, Rodimus set off into space with Prowl and Landmine with the help of some omnicons helping the innocent. Eventually he would meet up with Optimus Prime and even accept Optimus as his leader. He transforms into a "rocket-powered Cybertronian long-nose truck cab".
Transformers: War for Cybertron (DS)
See Hot Shot