Mendes' manager, Andrew Gertler, teased fans in an Instagram post of the artist's announcement from the show and captioned it, "Just about 1 week until this and some serious surprises."
One meaning of the cryptic caption that fans have speculated is that Mendes may be appearing in skits, something that musical guests like Donald Glover and Ariana Grande have done in the past.
Other fans have guessed that Mendes will bring out Taylor Swift in honor of the pop star releasing her single "Me!" last week with Brendon Urie of Panic! at The Disco.
Regardless of what the surprises may be, fans are freaking out at the post. One fan commented, "Andrew knows how to send the fandom into a panic for sure," with another saying, "SOME serious surprises? Not only ONE?"
Any time a surprise involving Shawn is involved, we're all ears. Adam Sandler will be hosting the episode that Mendes is performing on for the first time since he was a cast member, so we're in for a good episode already.