Sam Smith 'Carpool Karaoke' has a brilliant surprise ending

Ain't no party like a Carpool Karaoke party — especially if the party happens to get crashed by a whole bunch of other guests.
In the clip above, Sam Smith jumps in the passenger seat alongside James Corden before getting a surprise visit from a group he loves above all others: Fifth Harmony.
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Watch the video for the glorious singing, then stick around for Sam Smith's gleeful reaction when Corden pulls o