Talk:Mewtwo VS Shadow/@comment-26391314-20160624080145/@comment-26391314-20160624081913

^ According to this, Psych Up copies the foes changes in stats. It doesn't copy the moves themselves.

As for the reason why it doesn't work for Mega Evolution in gameplay, that's because Mega Evolving as an action isn't programmed into the game as a move. If it were, you wouldn't be able to use an attack afterwards.