https://www.theverge.com/2018/8/21/17763904/forza-horizon-4-halo-experience-warthog-cortana-master-chief

Forza Horizon 3 first introduced the ability to drive Halo’s famous Warthog nearly two years ago, and Forza Horizon 4 (due October 2nd) is taking that Halo combination a step further. Playground Games has worked closely with current Halo developers 343 Industries to create a miniature Halo experience inside of Forza Horizon 4. It’s essentially a side quest that teleports you into a drivable Warthog, while Banshees chase you along the beautiful route of the British countryside.

I got an early look at the Halo “experience showcase” at Gamescom today, and Cortana narrates the whole thing. The Warthog you drive is piloted by Master Chief, and a Pelican aircraft follows you along the route. News of this experience leaked out (see image below) last week, but Microsoft is still not providing screenshots or a video of it for everyone to see just yet.