According to the official website, each of the DVD volumes 1 - 4 of Kuruneko
will include an extra episode "Kuruneko-bin Tokubetsu-hen". They are > 7min long each and the volume 1 will be released on December 18th.
Matryoshka dolls of Kuruneko will be bundled with the DVD limited editions.
Picture of the items of the DVD limited edition
Kuruneko official website