In the definition of the toy camera, I think Christopher James summed it up well in the Plastic Camera chapter of his book Alternative Photographic Processes:

"Basically, in order to be considered a true and worthy toy camera the following qualities must be present: a mysterious shutter speed, minimal aperature control, no focusing control, a soft and romantic interpretation of subject and light, light leaks, and infinite charismatic charm."
I have to say that there's a lot of other valuable info in this book (that I truly enjoyed) and I'd honestly recommend it to anyone.