Well... To be honest, an inanimate object such as a castle cannot turn into an elephant, especially if it's an white elephant, although I don't think this is what you mean, will you please be slightly clearer with your definition of a "white elephant".
It will turn into Zekrom when you team plasma N's castle and talk to N.
It grows that way
Through a malfunction of metamorphosis.
You must have all badges. then, head to the elite four. after you beat the 4. you'll end up in N's castle. (Yeah he has a castle) Make youre way through the castle and you'll meat N. He'll summon. Reshiram-Black Zekrom-White Then, youre stone will light up and it will turn into one of the legendarys, depending on you're version. You will then battle it
Elephant it is still in the fridge
It was 1260.
The elephant turned back on the airport because he forgot to pack his trunk!! haa, haa, haa!
The Mighty Clouds Of Joy
It Must go to the King in the castle
to turn the wells bucket up
You have to go to the Elite Four and beat them. You will see N talking to Alder. Then Team Plasmas castle will appear. You go in the castle and in one room N is there. He talks to you and after his Reshiram appears your stone will turn into Zekrom and you battle him. P.S. Use a Master Ball
It turns vicious because you are chasing it.