讲述了小衰仔Martin和他的想象中朋友Sean之间发生的趣事Martin爸妈结婚20周年，带正太和小胖基友去都柏林找danny叔叔玩，俩男生帮叔叔去卖百科全书 飙到销售冠军，而这边夫妻俩在餐厅遇到了丈夫的前女友.. Sean (O'Dowd) is the imaginary friend of 10-year-old Martin Moone, the youngest child of a family living in a small town in Ireland. Martin has a unique perspective on life aided by an imaginary friend. His imagination comes into play both in his childish drawings, which come alive through animation, and in the ridiculous schemes he comes up with, against Sean's better judgement. With Sean's help, Martin negotiates life as the youngest in a chaotic, scatter-brained family.