I like the little cake in the bottom. It’s too small and has no relevance to anything else and who knows why it’s even there? I guess things like that just happen when you start messing with the time/space continuum.
This was most likely the work of someone who goes on the 4chan imageboard. No Weighted Companion Cube here. Just you, delicious cake, and something in between you and said delicious cake. Portals are just one of the ways to get around whatever is blocking you from the cake.
I would put the link up to a site that could explain it (although, you will probably not understand it), but it is inappropriate.