Strip Barracuda with Elizabeth and KalaI had these two play a new game, which needs some tweaking but I think it has potential. Here's how it works.
Each girl has a row of four face-down cards. They play rock-paper-scissors, and the winner gets to turn over her first card. She can choose to change the card for a random one off the deck or keep it. Then she guesses whether the next card in her row will be higher or lower. If she's right, she can keep going. If she makes it to the end of her row, she wins the round and the other girl has to strip. (She also has the option to "freeze" rather than keep going, but neither girl used this option so don't worry about it for now. Like I said, the game needs some tweaking.)