Bruce Banner canonically has 7 PhDs and honestly the fact that he periodically turns into a giant green ragemonster after spending that much time in academia without tenure is the most believable thing in the entire Marvel canon.
I tried to go for two back in the day but the university told me to just choose one. Still, I did eventually get formal postdoc credentials (the local equivalent to the Habilitation of the German academic culture, at the level of associate professor in US terms) and have worked as a university lecturer in both fields, and been the president of a learned society in a third unrelated one. Seven completed doctorates is a bit on the unbelievable side, though, even with high intelligence and ADHD.