When Kay decides to play superhero, she always comes up to me and says, "How can I help you, little girl?" and I try to think of stuffed animals to find or imaginary pets I've lost. (I like to get creative, "I've lost my pet zebra, Louie, please find him!") Honestly, I'm not that creative to be thinking up dozens of different scenarios of imaginary danger.
So this time when she brought out her cape (with the felt "K" super-glued to the back), I brought out little people figures and hid them in the tall grass. I told her, "Superhero, can you help me? My friends wandered into the forest and I can't find them." She jumped into action and quickly saved the day. Then she wanted to hide them so that I could be the superhero. (Oh yes, I did wear the cape!) We went back and forth, hiding them in different places.