Blow molding is a process in which plastic parts are formed by blowing air into a mold filled with plastic. The plastic adheres to the walls creating a hollow plastic part. Commonly blow-molded items include Shampoo and Soda bottles.
In the toy world, Blow Molding was commonly used to create cheap toys and bootlegs. The most prominent "real" toy are the Jumbo Machinder Toys from Popy (also known as Shogun Warriors).
Blow molding for toys appears to still be popular in South America.