We have definitely accepted some 'out in left field' explanations for characters to arrive in Smash, especially those who ordinarily wouldn't even have a reason to come.

We're perfectly fine with having Vaporeon show up in the Kraken Lake (which is now Kraken-less) by way of wormhole. We'd like it to be a one way trip in that manner, however. (Unless for some reason a future event features random wormholes all over the place - certainly not impossible.)

Feel free to contact us if you've got any additional questions and we'll be happy to further assist!