Published on SEGA's website in November of 2008, Sonic: Night of the Werehog is an ONA made to promote the release of Sonic World Adventure, also known as Sonic Unleashed in North America and Europe.

Sonic and Chip venture to an abandoned haunted house on a rainy night, soon to be caught up in the antics of two mischievous ghosts, who scare any of the house's visitors in order to take their picture and impress the ghost girl who lives there with them. Though they succeed in scaring Chip out of his wits, the two can't seem to make Sonic bat an eye at them. Furious, the two band together in order to get the best of Sonic; will he be able to put a stop to the duo with a little help from the full moon?