I was playing against a friends moltres stall deck with my Team Rocket ( Gym Heroes) deck.
I attach a grass energy to Rocket's Scyther and use shadow images. My opponent uses a (base) Mewtwo and tries to use barrier, does ha have to flip, if yes........
does he have to discard an energy card anyway and also even if he gets heads he still has to flip cause he didn't do damage to Rockets Scyther? Is this right?
 
 
Stephen Pritchard

Yes, he does have to flip, but the outcome of the flip means absolutely nothing.  Shadow images has the following two effects:

1) If Rocket Scyther is attacked, flip a coin

2) If the coin flip was tails, prevent all damage done to Rocket Scyther

So, yes you have to flip, but since Barrier does no damage to the Scyther, then even on a tails flip, all of Barrier's effects will happen.

Scott