On next week's episode of The Sing-Off, the 10 finalists will collaborate on an opening performance of Lionel Richie's "All Night Long," one of the greatest songs of all-time that hasn't yet been covered by the Glee kids. With so many a cappella groups still in the mix, it's understandable if you haven't found yourself a favorite this season. Here, the remaining groups get a pretty much equal split of the Richie song, that even rigid Nick Lachey won't be able to resist getting down to, while using colorful costumes to make it their own. But if you're looking for an underdog to root for, allow us to suggest Boston's North Shore, who make the most of their time spent relegated to the Non-Dancers Only balcony. Break out your maracas and air trumpet moves right now, you're going to need them for Monday.