The Godzilla franchise is,understandably, famed for its kaiju. Monsters like Mothra, or King Ghidorah,Rodan, and the titanic-G himself are the star attractions, or but all those kaiju need to come from somewhere. In several movies in the franchise,alien invaders have been responsible for unleashing monsters upon the world. Some of these aliens have been more memorable than others.
Source: blastr.com