Dr. Riddles (called Professor Riddle (ナゾナゾ博士 (Nazonazo Hakase?) in the original is a tall, old American man with a prominent mustache, a top hat with a floating question mark above it, a monocle and fancy black clothing. He often claims to be the “mysterious professor who knows all”, although he is clearly exaggerating. A frequent scene between him and Kido shows Kido explaining something that Dr. Riddles had told him earlier, only for Riddles to say he was “kidding”, which causes Kido’s expression to become shocked and negative.