Wild Manticore reads, "During faceoffs against this card, the challenger's opponent flips and additional card".
Typical pre-built decks which include these cards would be Applejack and Twilight Sparkle.
As a card becomes frightened it is turned face down, all counters are removed form it, and all cards attached to it are put into their owner's discard piles.So, this could be used to your advantage.
"When you play this card, you may reattach a Resource from one Friend to another."This is further explained on MLP CCG Wiki as follows:
"A player can use this card's triggered ability on Resources that were originally "played on an opponent's Friend/character" and attach them to their own Friend."