During her medley of hits, Abdul, 56, tossed her hat into the crowd ... and accidentally whacked the former "Dancing with the Stars" pro right in the neck.
Hough, 30, took the hit in the stride, dramatically gasping at the camera in the moment.
Posting a selfie in a neck brace after the show, Hough wrote, "The result of the honor of being hit in the neck by @PaulaAbdul's flying hat! Love you, babe!!!"
Abdul replied, "OMG I'M PEEING MY PANTS!!!! You know it was with love."
Abdul’s show-stopping performance included her smash hits “Straight Up,” “(It’s Just) The Way That You Love Me,” “Opposites Attract,” “Cold Hearted Snake” and “Forever Your Girl,” earning a standing ovation at the conclusion of her performance.