Sesame Street: Once Upon a Monster is a mini-game collection that uses the Kinect peripheral. It is set in a storybook world, where children help a new monster named Marco meet and interact with well known Sesame Street monsters such as Elmo and Cookie Monster. There are different activities to play in each of the six chapters of the book. Each activity makes use of the Kinect, from running in a race, to dancing, to blowing out the candles on a cake at Marco's birthday party. Each chapter has life lessons to learn, including friendship, sharing and teamwork.