In the game Indiana Jones and the Fate of Atlantis, there's a point where you need to find an object to continue. It could be in any one of about five different locations, randomly chosen each time you play the game.
One of those locations is inside a wax copy of an Egyptian cat statuette, which you melt in the furnace to get the object.
Whether the object is inside the cat or not on any particular play-through, you can pick up the cat and melt it in the furnace.
...or you can just pick it up and carry it.
If the object isn't inside the cat (and thus you don't have to melt it in order to continue), you can carry the cat for about 2/3 of the game before you hit a point where your inventory resets and you lose it.
Now, this is an item-collection puzzle game. Things you pick up are always going to be useful.
Objects that can go into your inventory will eventually be useful.
...except, in about 4 out of every 5 games, the wax cat.
There are a number of puzzles where a wax cat seems like it might be useful or appropriate, or at least amusing, but it's not. You're stuck with a useless wax cat in your inventory.
Everything about the game says you should eventually be rewarded for having a wax cat: it will be needed someday. But instead it just quietly vanishes from your inventory after spending the majority of the game as a red herring.
wax cat (n): Something in a game which appears important but is not, without actually being intended as a red herring.
3
Riven had a stationary wax cat in its first iteration; player testing made them take it out.
The game was big on atmosphere and showing rather than telling, so they put a book press next to the enormous wood chipper/boiler/pulper for making paper, to emphasize the purpose of the area for the locals.
... but many player-testers didn't know what a book press was, and thought it was a puzzle they had to solve.
I've wax catted my RPG players by accident on occasion.
One problem is that a lot of item-collection games make you wait a long time before you find the right use for an item, which produces a lot of emotional false positives.
