Plot: Motocross ""badass"" Carey Hart does a few stunts on 53rd St. ; Stephanie dons a Little Bo Peep get-up for ""CBS Mailbag;"" ""Arnold Schwarzenegger"" (Gerard) drops by; Brittany Murphy promotes ""Uptown Girls"" (and gets in a few good-natured rips on former beau Ashton Kutcher); Dashboard Confessional sings