Buffy crossover
Xander and Willow in this fic would be assumed to have known at least a bit about anime and manga pre-cannon. On Halloween, their costumes are a bit different, with long-reaching results.
Xander: Dressed as Saotome Ranma, unfortunately for him, now her, the curse gets triggered during the night, and Ranma was in girl form when the spell ended, but with the magic removed as Ranma is ripped away, the curse that allows the transformation _back_ also leaves, and even if it had stayed it would have turned her into otoko-Ranma anyway. On top of this, normal humans can't achieve the same level of martial arts power as Ranma, or at least not humans from Xander's dimension, Xander's new onna-Ranma body still has superhuman stats and an aura like a hanyou or something, but she can't fully or properly access Ranma's skills without training.
Willow: Dressed as Kinomoto Sakura, after having mastered the Sakura cards and made a couple of her own original cards. Willow doesn't come out of it with enough magical knowledge to create the new cards from scratch without the book and artifacts, but does get enough magical knowledge and control to really jump-start her magical training thanks to stuff Sakura had been tutored in by Kero and others, as well as Sakura's ability to make accurate and useful tarot divinations, not to mention at least faint memories of Sakura's experiences gathering and converting the Clow cards and making them Sakura cards and making her own original cards, plus, Sakura's presence in Willow jump-started Willow's obscene magical power in awakening.
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Dr. Strange at one point goes on a super long adventure at the behest of the cosmic entities he gets most of his power from through multiple dimensions, working with a bunch of other mystical heroes:
http://en.wikipedia.org/wiki/Vishanti
But who were some of the other soldiers in this 5000 year long cosmic war? What were some of the perils they faced? What worlds did they come from? Who were some of Dr. Strange's personal band of interesting allies? Well, they must have been quite powerful, not to mention likely immortal to keep up with something like this...
Dr. Strange's team-mates:
Hakubi Ryoko and Ryo-Ohki
Kinomoto Sakura
Lina Inverse
Dark Schneider
Takamachi Nanoha
Son Goku
Natsume (Sabrina, from Pokemon, her Japanese name)
Alucard (Hellsing version)
Willow Rosenburg
A team chosen because it is a bad idea to underestimate your enemies, and there is nothing wrong with a little overkill...
"Health, Learning & Virtue will ensure your happiness; they will give you a quiet conscience, private esteem & public honor." Thomas Jefferson (1743 - 1826)