If I take control of an opponent's character through an effect such as, say, Reek, do I also take control of any duplicates the character has attached and gain the ability to use them to save the character? Or can my opponent choose not to use the dupe if the character should die?

(3.25) Taking Control of
a Card With Attachments
Any time control of a card switches via a card
effect during a game, the new controlling
player gains control of said card and all
duplicates.

Unless specified in game text, the new
controlling player does not gain control of any
attachments on said character.