Rage 2 has a secret bunker, and the bunker contains an Easter Egg that is rather obviously about Elon Musk. You need to finish the Ground Control mission before you will be able to access this. You need Presidential access to get into this bunker, and you get that by playing through the Ground Control mission.
Elon Musk Easter Egg
The location of the bunker entrance is marked on the map above. Once you arrive, just head in the bunker door, grab the datapad on the right, then head down the elevator. Make your way through the bunker, picking up the datapads as you go. There will be four of them in total, and they are all pretty easy to spot, as they will normally just be lying on tables in the rooms you pass through. While you are down there, a scientist by the name of Elton Tusk will mock you, talking about how he is much smarter than you are. He seems to have been obsessed with space, new technology, and being rich. Sadly for him, his faith was to end up as a brain in a jar, forever bound to Earth.
Eventually, you will come to a room that contains a brain in a big jar of liquid, hooked up to machines. This is Elton Tusk. Make sure you look behind the brain, as there will be an Ark Chest hidden in the darkness there. When you get tired of hearing the brain talk about how great he is, take the elevator upstairs. There will be two more Ark Chests waiting for you there. And that’s it. You have seen everything the bunker has to offer, and can now get back to smashing up mutants and bandits.