Are those where the model thinks she's gonna be allowed to go to the bathroom, but then finds she's not allowed. Perfect example; the holding contest where model A wets herself so model B thinks she can go and relieve herself. Model A however restrains her until she wets herself! (I've deliberately left out the names in order to not spoil it for those who haven't yet sen the clip).
Suggestion: The model after having drunk a lot of water has a padlock on her jeans. Once desperate, she is given a key inside an ice cube. As long as she can get the key out she can attempt to open the lock and make a dash for the bathroom. But there's a catch; it's the wrong key!! And you don't know where the correct key is!! You find it though once she wets herself!!