Everyone knows Bruno Mars and Mark Ronsons hit song… except for Ellens audience.br For 13 incredible, eventful and sometimes life-changing seasons, Ellen has been making audiences laugh all over the world with her signature brand of humor .br The two had a dance-off for the history books!br Five-year-old Kai Langer has established himself as the foremost Bruno Mars cover artist, but check out how he did when he branched out for the first time!br The adorable 4-year-old crooner was back to put the moves on our host, and to make everybody in the audience melt.