They are being sold in large bags with nutrients and air etc. They are purchased this way and are supposed to be transferred to a suitable tank once home ( similar to goldfish at a fairground, or anything bought from a pet shop ). I don't understand where the keychain comes in? Nobody would surely attach them to carkeys LOL.
No, the bags they are being sold in are not large, they are around 1"-3", and are sealed, as they are intended to be permanent homes for these creatures (for a very short while, until they starve/suffocate to death, anyway). They are nothing like the ones you could win at the fairground.
They come with the keychains already attached.
And yes, people DO attach them to their carkeys -
(just a few of the many images you can find via Google...)