Julianne Hough returns to the show as a forth judge and four new pros join the cast. But the new quirky stars steal the show.

Smokey Robinson performs; a couple is eliminated.

The couples perform a variety of dances, including the cha cha, the rumba, and the foxtrot, for the judges.

A couple is eliminated; Sia performs as Maddie Ziegler and Allison Holker dance; Nico & Vinz performs.

It was all glitz and glamour in the ballroom as the remaining couples danced to songs from their favorite movies.

The couples dance to songs commemorating their most memorable year; Colbie Caillat performs.

The celebrities will switch partners, dancing instead with pros who were selected for them by viewers who voted on Twitter.

International superstar Pitbull returns to the ballroom and for the first time joins Julianne Hough, Carrie Ann Inaba and Bruno Tonioli as a guest judge MONDAY, OCTOBER 20 (8:00-10:01 p.m., ET) on “Dancing with the Stars.” Pitbull will kick-off the night with a steamy performance of his hit single “Fireball” followed by the nine remaining celebrities performing to a mix of his hits and personal favorite songs. Dance styles will include Salsa, Rumba, Foxtrot, Tango and Jazz. At the end of the night, one couple will face elimination.