Unless Fang Joker comes with new head parts for Trigger/Metal, then that's a custom. It's not the antenna. Look at the area around the Trigger eye in both pictures. The standard is rounded. The 'Fang' version is jagged. It's a different head. Also note the size of the head and placement of the mouth in each picture in relations to the Fang side. So either the set comes with head parts we haven't seen yet, or he painted the Joker side blue, and then used the rest of the Trigger body.