What, exactly, is this “it” here?
The image of riding Yorick’s back?
Surely the memory itself isn’t terrible. It’s the combination of the two things – the sweetness of a playfellow and imagining that playfellow not as he was then but how he is now – as if one could ride around on the back of a skull.
Hamlet is also transformed from those childhood days. He is a man, not a child, and he has known great sorrow. He has lost his father, seen his father’s ghost and sent his two childhood friends to their deaths in England. Not to mention being rescued by pirates – and discovering that his uncle is a treacherous murderous damned villain.
True, Yorick no longer has flesh. But as he died not long after these childhood games of Hamlet. he likely died much as Hamlet remembers him. While Yorick might have a difficult time recognizing the boy he once bore on his back.