Rocket League has had a ton of crossovers so far, but the most obvious one, the one that it should have led with, has remained elusive. Until now. Psyonix have announced that Rocket League will be getting brand new Hot Wheels themed DLC.
Rocket League will be getting Bone Shaker and Twin Mill III in February- both will be available for purchase separately, and both will come with six exclusive Hot Wheels themed decals to customize your cars further. The cars aside, free Hot Wheels themed DLC in the guise of customization options will be available to all players as random drops after a match- so you get to join in on the fun regardless of whether or not you want to spend money on virtual Hot Wheels.
You can check out a trailer showcasing just how well Hot Wheels will work in Rocket League below (surprisingly well, it seems). Rocket League is, for now, available on PS4, Xbox One, and PC. Psyonix have also discussed a desire to bring it to the Nintendo Switch, but nothing has come of that yet.