There were evil wizards, TV celebrities and undead beings, yes. But there were also walking memes, rare public expressions of queer life, wry commentary on the state of China and at least one bipedal cucumber — a colorful burst of pent-up energy and emotion in Shanghai’s first big Halloween celebration in years. In Shanghai, revelers have embraced Halloween, turning what started as a Western tradition into something distinctly Chinese. Over four days, they celebrated many of the things that Chinese censors normally suppress: elements of L.G.B.T. life, political and social…