That's a tough one. I'm not all that big on life-threatening excitement happening to me and that seems to follow the doctor pretty regularly. I'm sure that no matter my intention, it would somehow go awry. He seems like he'd have enough interesting stories to tell that it would be enough for me to have us both get hamburgers from In 'n' Out and then I listen to him talk about various adventures he's had over the years.
However, if risk-free time traveling is possible and I can affect the present by changing the past, I would go back in time to before George Lucas thought he'd do a digital rerelease of Star Wars with all the little changes and have him removed, preventing
from ever happening.
While probably not the best historical figure to remove, as the reasoning is really petty, I think the more monster-ish historical figures did something to change the way modern developed societies look at themselves. As terrible of men as Hitler and Stalin were, I feel they had a profound effect on modern discourse, and allowed us, as human beings, to see how much death and destruction one man in the right place can cause. While preventing their actions would be noble, as a species, we came out of their experiences aware of where racism and absolute power can lead and do whatever we can to try and prevent it from happening agani.
If risk-free time traveling is possible and I can't change anything, I'd love to get a tour of Versailles when Louis XIV was in power.