Cast as a Mask: Spider-Man and Peter Parker have separate accounts, ditto Green Goblin and Norman Osborn, and Owen and Puck. Hobgoblin and Roderick Kingsley seemed to be separate accounts, with the Kingsley account being his true identity, but "Kingsley" turned out to be Daniel (most of the time) and Hobgoblin was always Roderick Kingsley.
Chekhov's Gun: Too many to count. They do this a lot. The Crown of Thorns and the Spear of Destiny from the Radio Play become this in Grail Arc, then the Spear becomes this in the Mab arc. Then there is the throwaway scene when Lacunae first meets Thomeheb, and we see Tinkerer is working on something large underneath a tarp...a MONTH later we find out it's Thomeheb's Gateway to other Universes.
The Chessmaster: Osborn, Thailog, Xanatos, Thomeheb, Coldsteel, Dracula, and Doctor Octopus all have this.
Crossover Cosmology: Especially prevalent during the Mab arc, most of the Children of Oberon have quieted down lately, but we saw tons and tons of mythological figures fighting side by side...Many of whom weren't yet covered in the original Gargoyles.
Disproportionate Retribution: Lacunae Rahdan gets mutated into a gargoyle-mutate named Raksha and attempts to do the same to lots and lots of other humans. She also desperately wants to meet and please Demona. When she and Demona do finally meet, Demona smacks Raksha in the face with the steel butt of her bazooka, kicks her onto her stomach and rips her wings right off, tears out her tail, rips her horns right off her skull, and is briefly tempted to rip her glowing eyes out too, but tosses her off a building instead to slowly bleed out and watch the world fade as she dies. Demona does this not because Raksha ate a human being, not because she was making gargoyles look bad, no Demona did this because Raksha did nothing other than offend Demona's gargoyle supremacist ideology by merely existing.
Downer Ending: Occasionally, due to the fact that the RP largely takes place in real time. The Halloween Mini-arc was a definite downer, as Dracula turned the London Clan's only human friend (besides King Arthur) into a vampire, forcing Griff and Arthur to kill her, which was Dracula's plan all along, as he wants them all dead and she was the only one passionate enough to get a pro-gargoyle movement going. Worse yet, there are gargoyle claw marks on her mutilated vampire corpse.
The Dragon: The Erlking was this to Mab. And a damn scary one too. Also Coldsteel had become this for Demona.
Everyone Join The Party: This happens twice. The first time during the Grail Arc when Duval uses the Spear of Destiny and Crown of Thorns to literally subjugate every human being on the planet. Just about every active player had a cameo when this happened when every human dropped to their knees (some to hilarious results) results and chanted "Amen" and we all saw them again when Duval's control was broken. This happened again during the climax of the Mab arc. Every single character put in an appearance whether they were aiding in the fight against Mab, or narrowly avoiding collateral damage.
Evil Cannot Comprehend Good: Oberon, in response to Mab: It's why you lost the first time, Mother. What you continuously fail to understand.My power does not come from my magic. Nor Avalon. But from my true friends and allies. Something you'll never understand.*An army of Oberon's Children suddenly materialize on the buildings surrounding the Empire State Building.**A moment later, Brooklyn and Goliath Come charging in, leading two waves of gargoyles from the Manhattan, Avalon, and London Clans, and Spider-Man too* Triples as a Callback to the episode "The Mirror" and as a Big Damn Heroes moment.
Fan Disservice: Demona has Goliath chained in a dungeon (uh oh), strips down naked (so far, so good), sits on his lap and carresses him (admit it, fanboys, you wish it was you), and then she stabs him and proceeds to brutally torture him... Squick.
The Missus and the Ex: Brooklyn, Katana, and Tamora. But averted, the moment Tamora appeared back in Brooklyn's life, he went to Katana and told her everything.
Ms Fan Service: Demona. While very much in character, she has had more gratuitous nude scenes than any other character except for Raksha who went naked all the time after her mutation.
My Girl Is a Slut: It has been very heavily implied that Xanatos and Fox are swingers. It has also been implied that Roderick Kingsley and his arm candy of the week are regular partners. It has also been implied that the Osborns are no longer welcome at such parties the Xanatoses host.
Mythology Gag All the Oberon's Children love to do this. Like with Set and lettuce. Or with or Ares's "Little-miss-turns-rape-victims-into-horrifying-monsters" epithet for Athena.
Nightmare Fuel: Mab is this In-Universe. Casting a spell that causes every character to have nonstop nightmares for weeks on end.
Screwed by Formspring: The announcement that formspring was going to shut down grinded things to a halt for several weeks. Before that some dead characters had their accounts deleted due to inactivity.
Secret Identity: Spider-Man is Peter Parker; Dominique Destine is Demona; the Green Goblin is Norman Osborn; John Castaway is Jon Canmore; Hunter is Robyn Canmore; Cu Chullain is Rory Dugan; Owen is Puck, the Hobgoblin is Roderick Kingsley.
Shared Universe: It appears that Greg X's fanfic, Rhapsody, is set in the same universe, albeit 43 years down the road. A descendant of Cordelia appears in the Labyrinth in his 2198 fics, too.
Shout-Out: Often. To Greg Weisman's other works, and anything else that is appropriate for the situation. For example, Griff was wounded by HYDRA, but he brushes it off as "Merely a flesh wound."
Shown Their Work: The players for the Leader of the New Olympian Clan and Jove have very clearly done their research on Egyptian and Greco-Roman civilization.
Take That: The supremacist, violent, PETA-like PIT was an obvious shot at the cardboard cutout hippie PIT Crew from "The Goliath Chronicles" which has also imbibed its way into many "Gargoyles" fanfics, even those written by TGC haters.
Token Evil Teammate: Despite being a sociopathic, self professed Lord of Chaos reviled by most members of the Third Race, Set sided with Oberon in both wars against Mab, solely because his archenemy Apophis was supporting Mab.
The Unfair Sex: Betty Brant gets upset when Ned is nice to a waitress he's tipping. She cheats on him with Flash Thompson.
Valentine's Day Episodes: Just about every couple got in on Valentine's Day. Some had quiet dates, some went out, some hooked up, some had epic sex, some struck out, and some relationships were shown to be teetering on the edge of collapse. Throw in a marriage proposal too.
Van Helsing Hate Crime: The Quarrymen's murder of Montparnasse during the London Clan Exposed arc being a prominant example.
The Voiceless: Averted with Emily Osborn. She speaks and she's a cast-iron bitch. Played straight with Nought, Pistol (who both "speak" entirely in ellipses), and Claw (who uses emoticons). Hammerhead's chauffeur and Debra Whitman also have yet to speak.
Year Outside, Hour Inside: Interestingly done...since everything takes place more or less in real time, when the characters go to Avalon, they spend a lot of time there. The sun rises there, and the gargoyles spend two weeks (from a real world perspective) in stone sleep. Spidey is there too, and when he get's back he ends up in trouble with Aunt May and Gwen due to it being almost a month later.