So I was having a random matchup Double battle, and my opponent had a Darkrai and Volcarona. Knowing it would probably use Dark Void, I had my Gliscor use Protect and I had my Conkeldurr switched out in place of Espeon, who activated Magic Bounce. It only seemed to affect Volcarona, however. Perhaps this is an extra side-effect of Bad Dreams?
Umm, what are you talking about? I just tested out your exact situation, and Darkrai fell asleep alongside Volcarona.
This was most likely just a glitch in Showdown, and shouldn't be stressed over too much. Either that, or Dark Void missed (since it has 80% accuarcy)
Source: Above Replay