Yu-Gi-Oh! GX Episode 42: School Festival Duel! Trespassing Bla-Magi Girl
Episode 42 of 180 of Yu-Gi-Oh! GX, aired July 20, 2005, 25 minutes. Available with English subtitles and dub where released.
Episode summary
It's Duel Monsters Spirit Day at the Academy but when someone who looks remarkably like the Dark Magician Girl shows up for the annual Costume Duel Syrus goes gaga.