on the basketball court: it's more of a half court, but it's there. i think that much is proven. the myth portion is WHY it's there. there's a legend that Walt had to put it there to make it a 'sports arena' of sorts so he could get around some zoning restrictions. That portion isn't so much true. It's there, it's something to do in there, that's the deal with it. Kind of like there's a legend that the reason why Club 33 has an 'address' is because it was required to obtain a liquor license.
on pirates: the pieces absolutely shouldn't be moved around between visits (this would be the first i've heard of such a thing anyway). it is a stalemate although it's been argued by some chess players that there is no legitimate way for the pieces to end up in the position they're in. on top of that, it was created by marc davis but at some point, the pieces did lose their position (for whatever reason, I can't recall offhand) and they had to be reset except they could find no notes from davis as to which piece went where so it had to be re-created. davis also designed the ornamental roof of the haunted mansion which consists of various chess pieces (except for the knight)