Well my is a movie Darkrai. I checked the event page and it seems legit.
Its a fatefull encounter, I have done 3 random WIFI battles with it and I am work so I can't post it now.
Try it on a Wi-Fi battle on PBR. If it's not allowed then it's hacked.
Or you could post it's info here and I could try to tell if it's legit. (I have 6 legit movie Darkrai myself)
Remember that all Darkrai from New Moon Island are hacked.
By now Earth has a higher chance of being hit by a extinction level asteroid than you getting a Darkrai.
Not all..some are Glitched from the early Japanese releases remember...
So the only "real" legit Darkrais are from the movie in Japan?