He kind of ... jumped when he heard Mel getting knocked down, which either meant that his spell had met its target, or that she was clumsier than he thought. He thought the latter highly unlikely, though he wondered how he had done it. That was when he found out what spell he was under - Melofors. He was a pumpkin head! How amusing it must look for the audience.
Carl moved around the Arena, trying to make himself a harder target. That was difficult considering how heavy his head had become. When the Gryffindor cast her second spell, he knew that if he was struck by this one, he would be having a very hard time. "Protego!" He yelled and felt the spell shoot out from his wand and deflect the Bewitched Snowballs spell back.