Swift will assist during the knockout rounds, which begin in October.
The hitmaker is returning to the singing competition series as a mega mentor for the upcoming season and will offer advice to the contestants as they prepare for the knockout rounds in the show.
"I heard we have a mega mentor?" Legend asked Shelton in the clip, who said he heard the mentor is supposed to be a "big star."
"I heard it's supposed to be one of the most successful people in music," Legend added.
Legend pointed out that the mentor can't be Shelton since he's already a coach on the show.
Swift then casually walked out of a trailer and they all exchanged greetings. However, it took a second for Legend and Shelton to put two and two together. The lightbulb seemed to go off as the pop star's hit "ME!" then played in the background.
Check out the clip, below.
This will be the second time the Grammy winner has been an advisor on "The Voice" as Swift previously served as a mega mentor back in Season 7.
Swift will assist during the knockout rounds, which begin in October. During the Knockouts, Swift will mentor the singers as they are paired with a teammate and choose their own song to perform individually. The coaches select the winner -- however the artist not chosen can be stolen from another coach.
"The Voice" season 17 premieres Monday, Sept. 23 at 8 p.m. on NBC.
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