I saw this over the holidays and looked into it more. It is actually physically impossible to replicate IRL.
I don't mean the never ending bit I just mean getting it all to line up.
Take a look at the size of the slices and you will soon see why this will never work. The blocks that have been cut are manipulated during the animation to grow/shrink to fill the gaps that would otherwise appear.
The same illusion with a different presentation:
@DaveP This infinite chocolate bar animation absolutely bamboozled me, even with @LeightonJames helpfully pointing out that the pieces grow during their position shift. Then @VeryPC_Tom_B showed me just where they were growing and it started to become clearer. Anyway I went home last night still trying to figure it out and resorted to screen capping the key stages until I could fathom it. This is the result of my obsessive peering and manipulation:
and without guides:
You can't do this to me guys - I lost a whole evening!
You still didn't buy me a bar of chocolate which would do this though Al!
Thanks for the props @DaveP