South Park Easter Egg - Dying Light

The South Park Easter Egg can be found in Crane's room of the Tower. It's the same room that you woke up in at the start of the game, you can find it by taking the elevator up in the tower and going to the same floor as the Headquarters. Your bedroom is on this floor nearby the elevators.

Inside of your bedroom there are actually a couple Easter Eggs, such as the Call of Juarez Statue if you've completed the quest Dawud gave you early in the game, Gunslinger. As for the South Park Easter Egg, you can find it on the wall inside your room near the doorway. It's just a visual Easter Egg of:

1. Phase 1
2. ????
3. Profit

Pretty uneventful and you can just use my screenshot above if you're curious about the Easter Egg.