A: To review, if someone plays the Action Beam Us Up, if a player has the Teleporter in play the person with the Teleporter takes ALL Being Keepers into their hand. Since this is someone else taking your Keepers, you can counter that Action with It’s a Trap. This would cancel the playing of Beam Us Up (saving everyone’s Keepers).
It’s pretty clear what’s going on when the person playing Beam Us Up is the person who has the Teleporter: they’ve triggered the action, and they’re the one stealing your Keepers. It’s a Trap takes one of their Keepers. But what if the person who played Beam Us Up is NOT the person who has the Teleporter? It could happen! Maybe they were forced to play it because of Play All, or they didn’t have any being Keepers to lose, so they didn’t care. In that case, who do you get to steal from when you play It’s a Trap?
After some deliberation, Andy and I played it out, looked at the exact wording on all of the cards involved, and ruled that It’s a Trap targets the person who is stealing your Keepers, i.e. the person who is receiving them, regardless of whether they triggered the action or not. So you’d steal a Keeper from the person with the Teleporter.
This more complicated scenario looks like this:
Player A has the Teleporter in play
Player B plays Beam Us Up
Player C, who has Keepers which would be taken by A in this scenario, plays the Surprise It’s a Trap out of turn to cancel B’s Action Beam Us Up, and steal a Keeper from Player A, the person with the Teleporter.