The Departed X
This easter egg is found in the 6th Season, Episode 18.
In the episode, Kennedy and Heidi where Christopher and Tony get into a car accident and Christopher dies, you can see an “X” in the form of Christopher’s ‘Clever’ hat in the rear-view mirror.
This is a reference to a continuous easter egg throughout the 2006 movie, The Departed where an ‘X’ is always seen somewhere on the screen before something bad happens. The X’s appear as boarded up windows, support beams and even computer icons, but no matter what form it’s in, it never fails to show before someones death.
The easter egg is even further reinforced by the music used in this scene. Minutes before the accident Christopher puts in a CD which happens to be The Departed’s soundtrack and he and Tony have a short discussion about it. The song playing in particularly is ‘Comfortably Numb’.