Any obscure work of fiction or fanfiction would likely be fine as a casual test.

If you ask a model to discuss an obscure work it'll have no clue what it's about.

This is very different than asking about Harry Potter.

Yeah, that's what I've been doing as well, and at least Gemini 3 Pro did not fare very well.

For fun I've asked Gemini Pro to answer open ended questions about obscure books like "Read this novel and tell me what the hell is this book, do a deep reading and analyze" and I've gotten insightful/ enjoyable answers but I've never asked it to make lists of spells or anything like that.