Let's Rock is a MxPx compilation album of B-sides and unreleased material. "You Walk, I Run" was recorded by Jerry Finn during "the Ever Passing Moment" sessions, and "Make Up Your Mind" was also recorded by Finn and was released on "the Broken Bones" 7-inch. Both songs appeared on the "Responsibility" Australian import. The remaining ten tracks were previously unreleased and were self-produced. "Sweet Sweet Thing," an acoustic version here, was originally recorded with the entire band during the "Before Everything and After" sessions with Dave Jerden, then titled "Family Affair" and featuring slightly different lyrics. It was left off the album, although a portion of it can be heard in the album's "Before" and "After" tracks. Music videos were made for "Breathe Deep" and "Running Out of Time".