This video is about 5 minutes long: https://www.youtube.com/watch?v=fxLG8KZwmmE
They're calling it a live face change. It's definitely worth the 5 minutes it takes to watch. The video is a continuing evolutionary change of 'Paul's' face, starting in the late 1950's until 2016. It's really interesting to watch and not just because you can spot the different players of the character. If you keep your eyes on the nose, or the ears, or the eyes you can see how he's changed and, how many times he's been changed out.
You'll probably be like me and want to watch it over and over a few times just to spot how many JPM's you think you can spot.
I just found a 'live face change' video made about John Lennon. I'm posting it in his nook.