> BTW, GANs main use might be allowing almost fully unsupervised learning by extending small datasets with believable data.

I've wondered if dreams are basically this. Your brain uses its world-model-prediction subsystem to generate plausible inputs against which to train its action-generation-policy subsystem. Then, in real life, the action-generation-policy subsystem can react much more appropriately and quickly to real events.

Also, toddlers' stream-of-consciousness babbling when they first start talking. They narrate everything and more than once I've wondered if it's essentially them generating their own verbal training data. When they start talking to themselves their pronunciation, grammar etc. start improving much more rapidly.