In the show they represent Peter III of Russia (Nicholas Hoult ) as being Peter the Great's son. However, he was actually his grandson.
Ivan VI is portrayed here as a kid no older than eight, when in reality, he was about 21 years old at the time this series took place.
When Ivan shoves the cake in his mouth, some chocolate gets on his chin. In the next shot of him, it's gone, but in the shot after that, it's back and there for the rest of the scene.