Borden and Garsen Minx
Try as they might, none of the wizards can tell the Minx brothers apart. It occurs to them that they might have to 'bell' one of the brothers so they can keep them straight.
"Hello, hello," says [you assume] Borden. "Howdy, howdy," says [you also assume] Garsen. "What brings you gents here?" say both of the the twins in perfect unison.