I was in my local card store tonight and one of the people there mentioned some sort of combo to have multiple of the same planeswalker in play at once, involving some way to turn planeswalkers into non-planeswalkers to could avoid the Planeswalker Uniqueness Rule. He said he had some way to do this, but I didn't have a chance to hear what the actual combo was.
Now, I'm a bit skeptical of his claim, and can't figure out how to do this myself. I know Song of the Dryads can remove the type itself, but the side effects are counterproductive to the overall goal. On the other hand, I've seen ways of getting permanents both with every permanent type and no permanent type, so I can easily believe that some weird interaction could exist for this.
So in short, is there some interaction I'm missing that removes the planeswalker type from a card—or even better, all planeswalkers in play—to allow multiples in play?