Littlies are names for fairy babies, however this may be a slang form. They are born inside the Fairy Godmother, which when old enough will be able to go to the outside world.
When fairies are born they are called Littlies and resemble talking, bipedal eggs. They already exhibit the typical speech of the fairies. Until they can fend for themselves in the outside world, they spend their youth inside the Fairy Godmother who evicts them periodically. Once outside they eventually grow into a myriad of adult forms.