The characters engine noises are different in Relay Races in comparison to other modes. This was also present in Cars Mater-National (2007).
On the PSP version, in the cut-scene before the final race, Chick Hicks still says that he only used Candice, Stinger, El Machismo and the VINs to learn how to beat Lightning, even though the VINs do not appear in that version.
Since the game counts placing anywhere in the top 3 as winning and the PlayStation 2 version of Relay Races have only 2 teams, players are guaranteed to win.
On the PlayStation 2 version, Guido always turns his eyes in the opposite direction to which he is turning.
On the PlayStation 2 version, after completing Tokyo Mater, the voice clip of Mater winning is played twice. The 2nd one ends up replacing Mia and Tia congratulating Mater on his win.
Like in Cars Mater-National (2007), several characters have voice clips that are not tied to an animation. Sometimes, the voice clip is tied to an animation that does not match with it. A primary example is on the selection screen when Lightning says, "Oh, yeah! Lightning's ready." on the PlayStation 2 version.
In Cars: The Video Game (2006): The Video Game and Cars Mater-National (2007), most of the characters had voice clips of them reacting to Lightning driving past them at high speeds. Cars Race-O-Rama has these clips played even when Lightning is driving slowly or not driving at all.
The PlayStation 2 version of Reunion Rundown uses the same description as it does on other consoles, telling the player that they are facing Candice, El Machismo, Stinger and the VINs, but no VINs appear in the race.