From the back of the bookmark: The Official Star Munchkin Bookmark of the Weird Alternate Universe! (Guest Artist Edition)
You may use this bookmark in any game of Munchkin or its sequels. It may be used at any time. You may use only one bookmark (of any kind) per game unless you change sex. If you change sex, you may use a second bookmark. You may not use more than two in a game, no matter what.
(1) Show everyone the bookmark so they can satisfy themselves that it is what you say it is, because they may not be able to read it when you are done.
(2) Place this bookmark under a card an opponent has in play. (If that card is an item, it does not have to be equipped.)
(3) You may also gain the benefit of the card, as long as it remains in play. (If you have placed this under a one-shot card, you may only use this ability once, and doing so does not deprive your opponent of it.)
(4) If your opponent discards that card, for any reason, he gets to tear up your bookmark unless the card it was with is from John Kovalic's Munchkin Fu Guest Artist Edition, in which case he just keeps the bookmark.
(5) If your opponent still has the card in play when the game ends, you get your bookmark back!