Shelfwarmer

Shelfwarmer is a colloquial term for a toy that either fails to sell well or is over-produced, leaving residual quantities on store shelves for months or even years after its original release, generally far in excess of other toys from the same waves.

The term is doubtless a reference to the theoretical lessening of potential heat rejection from a shelving unit covered with a layer of packaged products, as compared with a bare shelving unit. In other words, Perceptor, it's a joke.

A related term is pegwarmer, used to refer to toys packaged on cards (which thereby hang on pegs), rather than in boxes.

From Teletraan I: The Transformers Wiki, a Wikia wiki.