(This is a joke don't actually put this down for your work) (these were all on the Internet)
US Goverment conspiracy: The moon landing was faked to hide the fact that the moon is actually a 2-D disk hiding ailen surveillance footage.
Foreign government: North Korea's government secretly has a anime creature that eats stuffed animals instead of food.
Large Corporation: General Mills's creator is actually a leprechaun who is still alive to this day and was the inpiration for Lucky Charms.
(I don't know any real ones)