Looks like Taylor's started a surprise guest trend.
All throughout the Jingle Ball season, singers have been jumping on stage together unexpectedly, delighting fans.
Last night, Tove Lo joined Demi during her Amalie Arena set in Tampa. They belted out Demi's big 2015 hit Cool For The Summer.
The divas capped off the performance with a shower of neon colored feathers raining down on the crowd.
— Tove Lo (@ToveLo) December 20, 2015
Lovato recently wowed the crowd with her unbelievable performance of Stone Cold at the Billboard Women in Music event.