This is not a tank.

In honor of April Fool's Day, check out the WWII era unit tasked with deceiving the Wehrmacht by impersonating massive allied armies. The 23rd Headquarters Special Troops used phony radio communications, carefully arranged lights and even inflatable dummy tanks (seen above) to divert German forces from intended targets. Informally known as the "Ghost Army" they played an important role in D-Day and the Allied push through Western Europe.

You can read more about them here, on wikipedia