Justin Timberlake may not have had a voice when he appeared on The Tonight Show on Thursday, but he did have his other half. Last week, Justin revealed that his vocal chords are severely bruised, forcing him to postpone some tour dates and rest his voice. The Tonight Show must go on, though, so the singer sat down with BFF Jimmy Fallon to promote his new book, Hindsight: & All the Things I Can't See in Front of Me. The pair got creative with their communication, and at one point, Jessica joined them to play "The Best Friends Challenge," which tested Jessica's and Jimmy's knowledge of JT. Watch the hilarious clip above, then check out the fun Halloween costumes they wore alongside their son, Silas.