Tottoko Hamutaro Anime Dechu! is a direct-to-VHS OVA released on September 15, 1999. This was the first attempt at an animated adaptation of Hamtaro, and consists of four short episodes.
The VHS was only released as a mail-order from the September 1999 issue of Shogakukan, and given away for free to Shogakukan staff with preschool children.
(Source: Hamtaro Wikia)