xxxHolic and Tsubasa Chronicle originally 'crossed over' as manga series, and the same is true for the television series and movie. In Tsubasa Chronicle, Sakura and her friends visit Yûko Ichihara, the Dimension Witch of xxxHolic, who later stars in the movie of the same name.
They are both based on manga by CLAMP that were written as stories that frequently mingled with each other. It was essentially the same two storylines from two different perspectives.
xxxHolic and Tsubasa Chronicle originally 'crossed over' as manga series, and the same is true for the television series and movie. In Tsubasa Chronicle, Sakura and her friends visit Yûko Ichihara, the Dimension Witch of xxxHolic, who later stars in the movie of the same name.