Under the city of Milwaukee, Wisconsin, there is a large underground government storage facility where surplus "government cheese" is kept. Under this facility is another facility in which people are grown in vats. These "vat people" can be recognized in public by their shockingly similar appearance to other people. If you ever see a person who has a striking resemblance to another person, they are most likely a "vat person".
Yo, did you see that guy over there? I could have sworn I've seen him before.
Yup, I see him. Definitely a vat person.