Oracle Text

Return target creature to its owner's hand. Then return another target creature to its owner's hand unless its controller pays 1.

Card Rulings

10/4/2004 The creature’s controller gets the option to pay when the spell resolves.
10/4/2004 The two creatures may have different controllers.
10/4/2004 Must target two different creatures.
10/4/2004 You choose on announcement which creature is the one that can be paid to prevent the effect. The payment itself is made on resolution (if at all).