I usually have trouble naming things but in this case it was fairly easy to come up with one.

The first thing I did was to check a thesaurus for words that represent the inconsistent and fickle nature of the product’s ‘personality’.

Out of these Temperamental really stood out as it incorporates the concept of something inconsistent and annoying, implies that the product is something playful and contains the words ‘temper’ and ‘mental’ to further reinforce the concept. My doubt with this as a stand alone name is that it doesn’t really convey that it’s a toy but in context and with a brief strap-line there will be no problem explaining what it is in the same way thousands of brands do.