Gödel and Leibniz
Gödel in his later age became obsessed with the idea that Leibniz had written a much more detailed version of the Characteristica Universalis, and that this version was intentionally censored and hidden by a conspiracy. Leibniz had discovered what he had hunted for his whole life, a way to calculate truth and end all disagreements.
I'm surprised that it was Gödel in particular to obsess with this idea, because I'd think that someone with Leibniz' smarts would have benefitted tremendously from Gödel's proofs, and it might have been a helpful antidote to his own obsession with making truth a question of mathematics.
And wouldn't it seem likely to Gödel that even if there were such a Characteristics Universalis by Leibniz, that, if no one else before him, he, Gödel himself would have been the one to find the fatal bug in it?
Starting Abstract Wikipedia
Gödel's naturalization interview