Keith Urban’s final night at Caesars Palace became unforgettable when his wife, Nicole Kidman, made a surprise onstage appearance. The Oscar-winning actress casually walked out during the show, prompting cheers from the crowd. “What’s your name?” Urban joked. “Nicole Urban,” she replied, playing along. Her reason for showing up? To retrieve his jacket. “I wanna get your jacket — you put it on the floor,” she said. The couple shared a laugh and found the coat together, turning a simple…