 Other permanent judges have included film director and choreographer Adam Shankman, contemporary choreographer Mia Michaels, pop music and dance icon Paula Abdul, noted youth dancer Maddie Ziegler, music and dance artist Jason Derulo, choreographer and tv personality Laurieann Gibson, and successful show alumni Stephen "tWitch" Boss and Dominic "D-Trix" Sandoval.Many earlier seasons frequently featured guest judges in occasional episodes, though this practice has become increasingly rare.These guest judge positions have typically been filled by choreographers who work regularly on the show (who in rare cases may also be former contestants themselves) and by iconic names from the entertainment industry.