James Corden really knows how to make our Christmas dreams come true. On Thursday night's episode of The Late Late Show, the host decided to give the audience (and, you know, the world) the best early Christmas present when he debuted a new Carpool Karaoke. In the video, which is his second one of the week following Bruno Mars, the legendary Mariah Carey drives around town with James to help him with his Christmas shopping. With the backseat packed with beautifully wrapped gifts, the two belt out her classic hit "All I Want For Christmas Is You." But that's not even the best part. A little over 40 seconds into the video, you realize that James got most of his Carpool Karaoke guests to sing the song with him throughout the year, resulting in one amazing mashup. Not only does Adele get totally into it, but Lady Gaga, Selena Gomez, Gwen Stefani, Demi Lovato, and "Saint" Nick Jonas also deliver. Watch the whole thing above, and be prepared to smile like a fool.