1. Go to the scene, sometime after exiting the store after Cloverfield decapitates the Statue of Liberty, where Hud says that he'll show the survivors his footage of Cloverfield (sometime around 23:00 minutes - varies depending on movie viewing program).

2. Pause the movie before the flashback after this, where Rob and Beth are on the bus to Coney Island.

3. Go frame-by-frame (or just keep pausing and hope you get lucky) and during one of the pink flashes shortly after Rob and Beth are talking you should see a still from the monster movie "Them!".