有些人甚至会使用魔术或穿些奇装异服,免不了会有人问他们在这些奇怪的装束背后的问题或故事.（直译是：这些奇装异服难免会让有些人问他们关于这些装束背后的问题或故事.there wearing应该是their wearing吧）
that 这里是充当引导词,引导定语从句,修饰something,所以指代也是something,这个从句相当于：something outlandish bound to have someone ask them a question or story behind whatever it is there wearing.