Hidden on the sprinkler model are the words "You can't find me." and a picture of a ninja.

World in Conflict contains a few references to other similar works.
One of the main characters in the game, Captain Bannon, is most likely a reference to Captain Sean Bannon from the 1987 best selling novel Team Yankee.
Both characters are high ranking US army officers in an Armor Company, and both fight in Europe during a "Cold War gone hot".

There are also plenty of references and similarities to the 1984 film Red Dawn as well.
Both have a large focus on the Soviet invasion and occupation of the United States, they include themes of resistance against Soviet occupation, and as previously mentioned both deal with a "Cold War gone hot" scenario.

The operation name for the Soviet invasion of West Berlin is even referred to as Red Dawn.

Collector's Editions of the game came bundled with an actual authentic piece of the Berlin Wall.