Yesterday's mention of sea changes reminds me of something else. I'd not realised until recently that the world being someone's oyster is another one of Shakespeare's coinages.
(I'd be surprised if he didn't have a claim to "how strange the change from major to minor" or "I've got a brand new combine harvester", too. Or "daddy or chips?")
Oysters are pretty, shiny things and I'd always assumed the phrase meant that for whichever opportunistic soul as was the subject, the whole planet seemed like a pretty bauble for the taking. If only you'd bother to try... You know, the heartening sort of thing they tell you in your career advice as a teenager (along with how it's absolutely impossible to make a living as a writer).
But there's more to it than that. The bloke who says it does so because he can't get any money out of his mate.
"Well," he says in Act 2, Scene 2 of the Merry Wives, "then the world's mine oyster. Which I with sword will open."
So people to whom the world is an oyster are less cheery doers with a bit of pluck and get-up, as violent, cut-throat thieves. Just to make the point, the bloke who says it is called Pistol.
I assume that's a nickname. It does make him sound like one of the lesser, hairyer, squawkier-laughing CB-tastic truckers in a Burt Reynolds movie.