Bob has a dog. You see the dog greet him exuberantly when he comes home, he introduces the dog to Alice when she visits, the dog enters into a couple of episode plots. Then the dog gradually fades from view. Entire episodes take place in Bob's home with no sign of his dog. You begin to wonder if the dog has taken to hiding whenever other people are around. Have the writers forgotten that he has a dog?
Then, unexpectedly, they mention the dog. Apparently he ran away a long time ago, or maybe was killed. The Fridge Horror sets in as you realize that Bob didn't even mention, much less mourn, the loss of his pet.
Basically, this is when the disappearance of a pet from a show's plot is explained long after the fact by the pet's death or disappearance. To qualify, there must have been no comment at the time - the only explanation occurs much later, well after they should have shown a reaction.
Contrast Chuck Cunningham Syndrome, in which no explanation is given.
- In the Tom Clancy novel Patriot Games, Jack got his daughter a Labrador named Ernie. It does not appear in any later book, though a comment in Red Rabbit, the next book in chronological (If not publication) order, implied that the dog stayed in America when the Ryan family moved to London for a year or so. No explanation is given for why they aren't reunited with the dog when they moved back to Annapolis.
- On Buffy the Vampire Slayer, Willow and Tara got a kitten, who was only seen in three episodes. An off-hand comment much later on suggests that this kitten was killed off-screen by an accident. It's not explicitly confirmed that the cat is dead, though, and the wording could be interpreted a number of ways.
Dawn: I told you, I don't leave crossbows around all willy-nilly...not since that time with Miss Kitty Fantastico.
- On Charmed (1998) the sisters had a cat named Kit, but after the first season or so the studio no longer had the animal. They covered with green screens and stock footage, but eventually stopped. Years later Kit returns as a human, having been rewarded for her work as the sisters' familiar.
- Joey and Chandler's duck and chicken from Friends. In the series finale, it is implied that they died and Joey was told that they were "sent to a farm."
- On Wizards of Waverly Place Max at one point admits that everything about the the wizarding world is true, "except for the Dragon Dog! I have no idea what happened to him!" The episode the dragon dog appears the Russos jump through some serious hoops to keep that little puppy-dragon. And then he disappears. And then all we get is Max's lampshade hanging.
- In Everybody Loves Raymond, Robert's pet bulldog Chamsky has a whole episode devoted to him explaining how he arrived and how he cost Ray nearly two thousand dollars. After this big build-up Chamsky the bulldog appears in maybe two more episodes and then nothing more is seen or heard.
- Averted in Something*Positive: Word of God says that the original plan was that Davan would (reluctantly) adopt Choo-Choo Bear, who would then disappear for years until a dark Brick Joke where they discover his corpse behind the sofa or something. Perhaps due to his popularity, he's remained a part of the cast, even though he should be pushing forty by now.
- Invader Zim has a variant: in one of his possibly-prerecorded messages to his children, Professor Membrane reminds them to feed the dog. This reminds the pair that hey, they used to have a dog, didn't they? and they take a minute to look around in confusion. The viewers, however, never heard of it before.