Knight of Cerebus/Playing With

Basic Trope: A character who heralds a series becoming Darker and Edgier
 * Straight: In a work that has previously been about the wacky hijinks of a small group of friends in a crazy world, Lord Cerberus kills loveable Alice shortly after his entrance.
 * Exaggerated: The world was a happy Sugar Bowl until Lord Cerberus arrived.
 * Justified: Lord Cerberus and his cruelties were always in the background; he's just now entered the main characters lives.
 * Inverted: A Magical Girlfriend arrives to help make the work Lighter and Softer.
 * Lord Penguin, an unusually wacky villain, appears to take Lord Cerberus' place as the main antagonist.
 * Subverted: Lord Cerberus arrives, and kills loveable Alice. The heroes obliterate him with Crazy Awesome and the Power of Friendship, and even resurrect Alice.
 * Alternatively, Lord Cerberus is set up as a force to be reckoned with, but is quickly subject to Villain Decay.
 * Double Subverted: But Lord Cerberus was just the vanguard for a far greater threat.
 * After Lord Cerberus has Decayed to Harmless Villain status, and everyone has forgotten that he was once a major threat, he proves himself a Not-So-Harmless Villain (or a stronger, more dangerous foe appears).
 * Parodied: Lord Cerberus is completely nuts; the work grows darker, but its Dead Baby Comedy.
 * Deconstructed: Because the world they live in hasn't seen anyone like Lord Cerebus before, they don't know how to react. Some panic, some Go Mad From the Revelation, and some become dark and edgy themselves during the long struggle against him.
 * Reconstructed: Lord Cerebus's arrival is a taste of the reality of life outside the show's Sugar Bowl. Some of the characters understand this, know better than to panic, and end up leading the struggle against him.
 * Zig Zagged: Lord Cerberus varies from being a pathetic Big Bad Wannabe to an outright Villain Sue Depending on the Writer.
 * Averted: Lord Cerberus is just another Harmless Villain.
 * Enforced: The author wants Cerebus Syndrome to start with a bang.
 * Lampshaded: "Wow, Lord Cerberus is cold. This Is Gonna Suck."
 * Invoked: A character who was once a Harmless Villain releases Lord Cerberus from his can to spite the main characters.
 * Defied: Someone in the team was ready for someone like Lord Cerberus to arrive.
 * Discussed: "Woah, that Lord Cerberus is really kind of a major buzzkill."
 * Conversed: "They killed Alice! It's Ruined FOREVER!
 * Exploited: A Harmless Villain uses Lord Cerberus's appearance, and major threat level to distract away from his petty crimes.

Back to Knight of Cerebus. You know, the site was a lot more playful before that trope came around...