Dennis Mulligan, Lad.2 A LOYAL PRACTICAL JOKER Maybe you saw his face inside the firetruck racing through Midtown streets. Or maybe you saw him marching in his blue uniform in the St. Patrick’s Day Parade. You’d remember that he was tall and broad-shouldered, with what Neil Skow, his lieutenant at Ladder Company 2, called “that fine Irish smile that he had.” And then you’d know a little bit about Dennis M. Mulligan, 32. He loved practical jokes but was also a loyal brother and son, a pal to his nieces and nephews, who called him “Superman.” He liked to tell his sister, Patricia, that he was fireproof, though he once scorched his fingers on someone’s birthday candles. He would visit the sick, including one woman who was severely depressed. “He would go to her hospital bed every day, and he wouldn’t leave until she laughed,” his sister said. Off duty on the morning of Sept. 11, he jumped on the ladder truck to help. Another firefighter remembered seeing him with a couple of other men from Ladder Company 2, escorting frightened workers from the lobby of 1 World Trade Center. He still had “that Mugsy smile,” the firefighter said, which seemed to reassure them.