The BIG difference between the two is that one is pregnant and the other isn't!
So looky-likey Heidi has taken to wearing a 'false bump' so she can stay employed as the real Kate's doppelganger.
The 32-year-old former waitress has spent the past 10 months as the Duchess of Cambridge's double. Now she has had a bump made in various sizes' to look as convincing as possible.
Heidi from Corby, Northamptonshire told the BBC: "As Kate grows I will too - to be authentic I thought it was important.
"It's difficult at the moment as she's not big enough yet to change her entire wardrobe so it's difficult to see how she's going to dress it."
Heidi swapped her £6-per-hour restaurant job to become a £650-per-appearance Kate double last May. She now travels the world as a royal look-a-like.
She said: "To have done 12 years of something you know and then to leap into an industry that gives with one hand and takes with another is difficult, but I'm just really happy and feel blessed that I did."
The mum-of-two revealed she has to buy the same shoes and dresses as Kate to look authentic. But she has also perfected the Duchess' mannerisms, how she stands - and even how she talks to William.
"Things like that are all very important if I want to be the best," she said.
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