Found by Malikowicz: • Video
The way this glitch works, is by loading a save file with Johnny's race coin unlocked in the Baxter building, then loading a different save file. The coin will now appear in the other file regardless of your progress in the story* and city goals.
The first Johnny race coin is unlocked after completing 5 easy races. After that, you can ahead to the next Johnny races immediately.
Is there anyone here who has this game on console and can confirm whether or not this glitch works on console as well?
Should this glitch be allowed in the leaderboards? I think so. Should it have it's own subcategory or just replace the current route? I'm not sure, but I'm leaning towards the latter option right now.
* Does not work on save files made before the intro Johnny race.