Sure, a bowling ball seems like the obvious aesthetic choice as far as special packaging for this landmark edition. But I happen to know that the decision-makers responsible for this collectors item ran through a laundry list of other potential encasements and dispensed with all of them for various reasons before arriving at the perfect simplicity that is the bowling ball. To wit:

A large severed toe (deemed too graphic)
A coffee can/urn (too depressing)
An animatronic Pomeranian (too technically complicated)
A large J (too controversial)
A Creedence tape (too nostalgic)
A miniature oriental rug, complete with pee stain (too expensive)
A briefcase with dirty whites inside (too gross)

I think they went in the right direction with this, don't you?