The crossover: BTVS / Magic Schoolbus / Dr. Who

The Concept: The world's greatest (and strangest) teacher Ms. Frizzle has something in common with the universe's most prestigious doctor, Dr. Who!

At some point, be it pre, post or during BTVS, one or all of the Scoobies meet Ms. Frizzle and are introduced to her... unique teaching style. Somewhere in their journey, however, the Magic Schoolbus takes a detour from the scheduled field trip and runs into a 'sister ship' that looks like a... Police Box?!?

Some possibilities as to why the Scooby / Scoobies are involved...

The idea is simple: Xander's somehow become a biblical figure from the Old Testament (anything up to The Gospels).

The How, is easy: reincarnation, YAHF, Time Travel, your call. This can go either way, Xander becomes the figure, or the figure really was Xander thrown back in time.

Some suggestions for who Xander becomes:
Jonah - Swallowed by the 'great fish' for refusing G-d's order to go to the city of Nineveh to prophesy against it.
Abraham - Risked it all on faith. Also, the man HAGGLED WITH G-D over destroying two cities!
Moses - Led the Israelites out ...

We've all seen different ideas about Xander having a last minute change of heart about his outfit, or that his soldier's uniform is from someone in another fandom, but I've only seen a few where Buffy's outfit turned out to be someone of importance.

Now, anyone who's a fan of the Honor Harrington series knows that every once in a while the unabashedly prudish people of Grayson like to make everyone's favorite Steadholder / Countess / Admiral get fancy in a ball gown.

So what would have happened if the 'Lady Elizabeth' outfit had been changed with a simple addition of a gr...

So I was thinking about what character to go as for Halloween and I came across the thought of going as Duncan Macleod.

Then it hit me today when I was thinking about how awesome it would be if we 'pulled a Buffy' and had our costumes possess us, and this idea came out. Unfortunately I know I don't have the skills to do it justice, but I know the spattering of Highlander fans on this site may appreciate it.

The challenge is this:
Xander went to the Costume Shoppe (Ethan's costume shop) and for some reason instead gets a plastic sword and raids his father's closet for ...