A: For reference, Floop a Keeper reads:

Discard one of your Keepers to also discard one of an opponent’s Keepers and to take a card at random from that player’s hand and add it to your own. This is called flooping. If the Keeper you discard to floop is Mr. Pig, discard ALL of the other player’s Keepers and take ALL of the cards in that player’s hand.

Well, this does seem a bit ambiguous, so I checked with Andy, and he says that when you floop the Pig, it has to be your Pig. Think of it this way for the wording on the card: the flooping is the discarding of your own Keeper… which then triggers the damage to your opponent, either minor or major, depending on which of your own Keepers you floop. Thematically, the scene that this comes from involves a player flooping the Pig they own, dealing a crippling blow to the other player. So the Pig must be in your possession in order for it to be you flooping the Pig.

If you check out that episode it’s clear one can only floop something one owns. Part of the subsequent damage (discarding a Keeper) just happens to be what you do to your own Keeper to floop it (discard it) so it’s certainly a bit confusing.

For funsies, here’s a link to the applicable scenes. To see the whole game (both instances of Finn flooping his Pig) you have to watch two clips, in this order:

Synopsis of whole episode:
http://adventuretime.wikia.com/wiki/Card_Wars_(episode)