That is the highest quality of milk damnit. That is milk so good the calf may never graduate to solids.
I recall a while back the claim that all the Straw Hats were inspired by other stories. The only ones I every saw any sort of suggestion that might be so though were Chopper (Rudolph the red nosed reindeer, ostracised by his kin for being a freak) and Usopp (Pinnochio, the liar who wants to be a real boy man).
These days I think there's very little from pre-Grandline he could not handle alone. But he's still one of the weakest of his peers. His achievement will likely either be outfighting his dad or taking out someone well out of his league in a manner he feels is is manly.