Both dogs are Chihuahuas, but the tiny one is a real Chihuahua while the giant Chihuahua is a cross between a Chihuahua and an Australian Terrier.
Chihuahuas R Us: Vancouver, BC
The most popular names for Chihuahuas are: Attila, Paco, Pedro, Hercules, Spike and Paris according to Dr. Google.
Mexican names are understandable but Attila, Spike and Hercules? Paris, it must be because of Paris Hilton used a Chihuahua as a fashion accessories. Dogs have been fashion accessories for the last five hundred years when only Kings would have personal, non-working dogs but never Chihuahuas.