They're small, can't grow bears (usually). They're also generally somewhat playful and shy. They generally fear things they don't know, which can be seen by the fact they don't travel far beyond their homes. They are pretty care-free and not bothered by external event, and fairly joyful. They live relatively simple lives and generally seem to be easily amused.

They don't behave exactly like children, but they do have qualities we associate with children. That, plus their physical characteristics, I'd say childlike is a decent description, particularly if you're just trying to insult someone for hanging around them.