Wherever there are Orcs or Goblins, there are tiny greenskin Snotlings. It is a common belief among humans that Snotlings grow into Goblins and Orcs. Given that all greenskin settlements are overrun with the things, this idea does seem to be a perfectly reasonable assumption. Another equally likely explanation is that Snotlings are just the smallest of a whole range of very variably sized and shaped creatures. No Orc or Goblin would draw a distinction between a largish Snotling and a smallish Goblin. To an Orc, anything smaller than him is a "Grot" to be kicked and abused, while anything bigger is a "Boss" to be avoided as much as possible.

Snotlings may be included in your Orcs & Goblins army as a Core unit choice.