xxxHolic

This is another manga, anime from CLAMP that ties in with Tsubasa: Reservoir Chronicle and Cardcaptor Sakura.
xxxHolic has been serialized in Kodansha's Young Magazine since 2003 and published in volumes under the KC Deluxe label.
It's published in the United Kingdom by Tanoshimi and in the US by Del Rey Manga.
On August 20, 2005, an animated movie, xxxHolic: A Midsummer Night's Dream, was released in Japan. The movie was released on DVD on November 24, 2006 and TBS (Tokyo Broadcasting System) began airing a TV animation series April 6, 2006 in Japan. Funimation Entertainment obtained the rights to both the movie and TV series for distribution in the United States.
At the end of the second season run of the anime, a special episode was announced for a DVD-only release. It will be bundled for release with volume 14 of the manga on January 16, 2009.

In the manga there are references to Cardcaptor Sakura, Tsubasa: Reservoir Chronicle, Magic Knight Rayearth, Legal Drug, Kobato, Chobits, Lupin III and Cat's Eye.
In the anime, there are references to Ōkiku Furikabutte (a baseball manga) and Ghost in the Shell: Stand Alone Complex.

"Watanuki's Sixteen-day-old Moon Grass Story" was released as a video game in Japan for the PlayStation 2 on August 9, 2007.