Dr. JT Goodenough has this ability:
React, Boot: At the start of the game, search your deck for two different non-Unique Gadget Weapons and reveal them. Your opponent chooses one to discard. Attach the other to one of your dudes, paying its ghost rock cost (without inventing). Discard a card.
In multiplayer, which opponent is "your opponent" who chooses one card to discard? Does the owner of JT get to pick which one?