At the start when Shep awakes from the nightmare, you hear the intro to Tupac Shakur's "Pain" - "I Couldn't help but notice your pain" - "My pain?" - "It runs deep, share it with me!". This voice-over is from Star Trek V: The Final Frontier (1989).
In the movie's first scene Shepard and Nutso are playing ball on a rooftop with a huge wall and glass window behind the basketball hoop. When Nutso falls off of the roof the wall completely disappears.
When Kyle is cheering in slow motion at the end of the movie, while "regulators" was playing, you clearing see Kyle accidentally hit heads with another one of the players