Greatest films with mannequin/human hook-ups: Mannequin (1987), Mannequin: On the Move (1991), Lars and the Real Girl (2007)
Mannequins, including human-sized blow-up dolls, are sold around the world every day, so it was bound to be exploited in a movie to explore certain facets of love and relationships.
The thing about Mannequin is that it's really just about how depressing it is to work in retail. You get the job because you need it, your boss hates you automatically, and you work the worst entry-level job. Then, since you're so depressed and lonely because of the stock-boy hours, you fall in love with a mannequin who you swear comes to life.
In 2007's Lars and the Real Girl, Ryan Gosling, the guy every other girl currently wants to jump, actually managed to make audiences empathize with his relationship with Bianca, a life-sized sex doll, that he treated as a real woman. That's the power of Gosling.