Credit: WENN.com Photo: Rock and Roll Marathon

More twists are coming to Dancing With the Stars Season 17! The final eight couples will do their usual routines on Monday, October 21 — here’s who is dancing what — but they’ll also compete in this new “Switch-Up Challenge.”

According to ABC, the challenge is a “fresh take on a dance marathon where couples will compete side by side, in two rounds, with no prior knowledge of dance style or musical accompaniment. One by one, the judges will select couples to be tapped-off/removed from the dance floor. Extra judges' points will be awarded to couples based on longevity.” It sounds like that’s going to openly favor people who have previous dance experience — since they’re more likely to be able to wing an unknown dance style — as well as younger contestants, who tend to have more stamina and often do better in marathons.

Credit: Instagram Photo: Ariana Grande

Also, as we previously mentioned, former DWTS pro Lacey Schwimmer will be returning to the ballroom, along with her brother Benji, for a big opening number featuring the entire cast.

And since we now have time in the two-hour program for more Results Show-style elements, musical guests Ariana Grande and Mika will perform their duet “Popular.”

Also like a Results Show, someone will have to go home at the end of the night. Do you have any guesses on the exiting couple? It’s just a guess, but we’re thinking Leah Reminiand Tony Dovolani may not be happy with the new “Switch-Up Challenge” and could be in danger.

Catch the next episode of Dancing With the Stars on Monday, October 21 at 8 p.m. ET on ABC.