When you return to CyberLife as Connor, listen closely to the security system as it scans you at the door. It’ll reveal that one of the guards escorting Connor is designated Agent 47, which is a nod to the protagonist of the Hitman series.
Demo Kara In The Junkyard
During the junkyard scene in the Broken chapter, explore the area directly next to the slope you have to climb to escape. You’ll find a discarded Kara model, who will be singing in Japanese. This indicates that she’s the same android model who was featured in "Kara," the tech demo from which Detroit: Become Human originated.
Heavy Rain Origami Birds
During The Painter chapter, take the time to fully explore the room. In the far corner behind Carl’s table, you’ll find a couple of large origami birds on one of the shelves. These are identical to the ones found in Heavy Rain, another game by Quantic Dream.
Quantic Dream Films
During the Battle For Detroit, there is a cutscene where Kara picks up a gun from the ground. As she holsters it, pay close attention to the movie theater marquee that’s shown above her and to the right. The movies listed are Heavy Rain, To Infinite and Beyond, Nomad Soul, and Jungle 2. Aside from the last one, these are references to Heavy Rain, Beyond: Two Souls, and Omikron: The Nomad Soul, all of which are games made by Quantic Dream.