Who writes the scripts for Stewie? There are some very intelligent stuff he talks about, for example in the episode where he creates the Universe and talks about temporal causation. Not to mention a number of other episodes that one just learns from, as they are mostly accurate. Who is the brain behind it, or have they consulted SMEs for some of the scripts?
There is a long list of writers for Family Guy throughout its seasons. They write Stewie's dialogue, as they do for all of the other characters. Stewie is characterized in the frame of a prodigal genius stuck inside the body of a toddler and is (at least initially) hellbent on 'revenge'. The stuff Stewie talks about can easily be googled and is not always scientifically correct.
The list of writers for family guy is here. https://en.m.wikipedia.org/wiki/List_of_Family_Guy_writers