Seamus blew everything up. And he was always quite embarrassed when his face was blackened with soot and his hair was standing up on ends, singed from the fire. He considered himself a huge fiasco, everything he tried to do, he just ended blowing it all up. But Seamus' little tricks, intentional or not, always made Dean laugh. It was always fun. And besides, Dean thought Seamus literally looked smoking hot when he blew stuff up ;)
