I don’t know if this counts as ‘famous’, but they’re historical and in myths, so that’s kind of ‘famous’ right?
I would pick Viracocha, who the Incan’s thought of as “bringer of civilization”. Supposedly he taught the pre-Incans agriculture, mathematics, astronomy, and technological skills. I’d want to know if he is actually Kukulkan (Mayans), Quetzalcoatl (Aztecs), Enki (sumerian), or Osiris (Egypt). All these other cultures have the same theme or idea that this person brought these things to their civilization. It would be interesting to know if this person actually existed because right now this person (or these people if they’re not actually the same) is/are considered a legend. Provided that they were real I’d want to know if this is the same person is the same as the others, where he/they came from, why he/they came to these places, and then I’d ask a ton of random questions depending on the depth of his/their knowledge.
If that doesn’t count then Carl Jung to talk about psychology and his interest in astrology. I’d also want to pick his brain about certain personal questions about myself and see how he would psychoanalyze them. Maybe I could find something out that would be useful for my personal growth.