I miss the old days of LJ. I like looking at Tumblr, but it's like getting sucked into a black hole. I come out two hours later, dazed from the pretty with no idea how I spend so much time there. And I can't keep track of discussions at all. Unless you happen upon another response, it just kind of...disappears into the mists of time.

As for your story, witches could summon anyone for any reason, right? They'd just have to have a reason. If you're looking for a connection with Merlin and Arthur, what about using the witches played by Spike and Cordelia? (Don and...??? You know, from Buffy.) They're both over 900 years old, so maybe they pull them to our time for some reason.

The other thing could be some bumbling baddie who raised a dragon or something, and to correct their mistake, they pull Merlin and Arther to fight it?

You could really have anyone or anything who read the legends of Merlin and/or Arthur try to pull them to our time for any reason. They just have to be stupid enough to think that the guys will help them, not function under their own free will.

Or maybe Rowena knew them back in the day, and Crowley pulls them to the present to deal with her. Or his son does..?

Good luck! If you can figure it out, I'll read it! :)