South Park made fun of this trope in the mock Cliffhanger at the end of the episode "Professor Chaos". The episode was spent focusing on Cartman, Stan, and Kyle's search for a new fourth friend and Butters becoming Professor Chaos and trying to destroy the world. The announcer recaps these plot threads as the episode reaches the end, then out of nowhere goes through all the motions of a someone-will-die cliffhanger (complete with six possible victims — Chef, Mr. Garrison, Jimbo, Officer Barbrady, Ms. Choksondik, and the Mayor) and then immediately tells us the resolutions of the loose ends, including who died (Ms. Choksondik, though Chef does die in a later season), and after the corpse played a small (but important) part in the very next episode, the story ends there.
The very first commercials for Season 1 also played with the series' early Running Gag, capping off each short description of the episode's plot with "...and Kenny dies!"
The season 1 finale episodes of Avatar: The Last Airbender were the subject of much hype, since the trailers promised that "a sacrifice would be made". As it turned out, the short-lived Princess Yue was the victim. However, a surprise twist came in the form of another death, namely that of recurring villain Admiral Zhao.
The 2003 Teenage Mutant Ninja Turtles did a kid friendly version of this for the season three finale: "You'll never see one of these characters again!". In the end, the character written out was Shredder, who was captured and sentenced to exile on an ice asteroid. And then Turtles Forever happened.
Chaotic had possibly the most annoying one ever. During one of the episode's preview, the narrator claims "And one of these characters... will be no more," accompanied by pictures of all the main characters. However, if one looked fast, you could see that, in addition to all the real characters, there was a picture of Maxxor, a card owned by the main character that would most likely be fairly easy to replace. Sure enough, he lost the Maxxor card in that episode, and all the main characters got out unscathed.
The Comedy Central series Drawn Together had an episode that was advertised with lines such as "someone will die" and images of the main characters. In the end it turned out to be a pizza delivery boy who had never been in a previous episode and whose death was relatively uneventful, a clear parody of this plot device.
Not to mention the episode in which a heartbroken Xandir (after his coming-out) tries to commit suicide, repeatedly, because as an video game action character he has to whittle away his Extra Lives (all 49 of them, and he gets more all the time) before he can kill himself for real. After spending the entire night killing himself and resurrecting, and killing himself, and... the others talk him out of it just when he is down to the last life.
And of course, this trope is meaningless to Drawn Together anyway, since major characters often get killed and are brought back in the next episode without explanation.
The Simpsons played it for real when they ran ads claiming a character would be killed off, only for it to be the less-than-central wife of Ned Flanders; there were several false alarms before the actual death (i.e. there's a crash at the racetrack, and a wheel goes flying and slams into Lenny Leonard, causing the spectators to gasp...and Lenny gets up and says "I'm okay!" to the spectators' disappointment.)
The Season 26 premiere, "Clown in the Dumps", was hyped up as having a character voiced by an Emmy award winning cast member die in it. While it was initially assumed by many to be someone like Krusty or Sideshow Bob due to the title, it turned out to be the very minor Rabbi Krustofski who kicked it.
Clone High parodied the trope with a blatant speech by the narrator during a slideshow of the main characters looking shocked: "Tonight, one of the clones you've grown to love will be horribly killed! (A picture of Ponce de Leon - who had never been seen in the series, and didn't actually have a name up until that point - flashes) This isn't some cheap ass stunt where we lamely introduce a new character (Ponce flashes again) just to kill him off! (Ponce, again). A clone dies tonight! (Ponce smiles at the camera) "
Made funnier by Ponce's constant Tempting Fate during the actual episode, as well as the string of extremely forced statements to the effect that the newly introduced Ponce was in fact a long-standing and widely liked presence at Clone High. The point is made most blatantly when Ponce pulls a stunt causing an actually familiar face to comment:
Julius Caesar: Oh, Ponce, you're a regular character!
And it was a horrific death at that.
If you'll notice, when the slideshow is flashing through, most characters are shown with a light-colored background, while Ponce's is blood red.
Sort of done in the fourth season of Winx Club, you see, in episode 23 the Winx receive the final gift of destiny from the Eternal fairies, which can be used to bring one person back to life. The Eternal fairies also tell them of a prophesy that apparently more than one person would die. The preview for the next episode also made it pretty clear that something bad was going to happen. In episode 24 the evil shapeshifter Duman turned into a monster and attacked the specialists, and Nabu was forced to kill him in self-defense. Later Nabu dies after using up all of his magical energy to close a dark abyss that the evil wizards had created in order to seal the Earth fairies away. Oh, and the last gift of destiny? Ogron, the leader of the evil wizards stole it and wasted it on a wilted flower.
Advertised constantly in the season 9 premier for Family Guy. To no one's surprise, the one to die is Stephanie, an annoying new character Quagmire brought with him, designed specifically to annoy everyone. However, the body count continued with James Woods, Muriel Goldman, Derek (Jillian's husband), Priscilla (another new character), and finally, Diane Simmons, who was the killer. And surprisingly enough, it stuck, come the next episode, they're all still dead.
In addition, one of the main 6 cast was slated to die in the 12th season. Brian briefly was dead, but it was for only two episodes, and was completely retconned shortly afterwards.
On the hundredth episode of American Dad!, the opening informs us that one hundred characters will die in this episode, and a counter appears at the bottom. It keeps popping up when someone is in mortal danger, but then disappears when nothing happens. Halfway through the episode, it goes up to one when Stan kills a dog, and then a bus full of minor recurring characters goes off a cliff and brings it up to 97. Three more minor characters die over the course of the episode to bring it to 100.
American Dragon: Jake Long had the promo for the episode Homecoming claim that "At least one of these characters will be...no more". Which is a little ironic, seeing as the writers planned on killing off recurring ally Sun Park, but the channel executives told them that her death would be "too dark", only to advertise the death of The Huntsman and the rest of the Huntsclan.
King of the Hill ended its second season with a cliffhanger when the Mega-Lo-Mart exploded. Leading up to the third season premiere was a promotional campaign, stating that one of the following characters would die: Hank, Luanne, Buckley, or guest star Chuck Mangione. It was Buckley.
On Celebrity Deathmatch, Stacey once received a prophecy that one of the Deathmatch crew would die before the end of the night. She tried to warn everyone but they laughed it off. By the end of the episode, despite a few close calls, none of the crew was dead, so it seemed like the prophecy was bogus… until Stacey spontaneously combusted.