I read the Bulbapedia entry on Altering Cave
and it said you can get these Pokemon through the Mystery Gift at a Nintendo Wonder Spot.
However, the page also says:
Despite this, no country has ever held an event to make use of this hidden feature.
This leads to the question: if the Nintendo Wonder Spot event never
took place, then how does Bulbapedia know that these Pokemon can be found there?
I've read in other threads that something with the e-reader makes the Altering Cave work. However, the Bulbapedia page makes no mention
of using the e-reader to change the Pokemon in the Altering Cave, which can lead to the conclusion that the e-reader thing was a false claim.