Text (UH): Open a sealed Magic booster pack, reveal the cards, and put one of those cards into your hand. (Remove that card from your deck before beginning a new game.)
Any physical (not online) booster pack is legal, even if cards from that expansion are not normally legal in the game you're playing. [Unhinged FAQ 2004/11/15]
If Time Machine is used to hold the card, it is not removed from your deck at the end of the game, but instead follows Time Machine's rules. [Unhinged FAQ 2004/11/15]
All tournament formats have banned cards from Unhinged.