@BaronOfHair said:

He doesn't speak perfect grammar.

His genius may be limited to physics. We've all known folks like this in real life

That is true for some. Young Sheldon is better at showing that isn't the case. Adult Sheldon is still a germaphobe.

He bought a turtle even though they're known carriers of salmonella. No true germaphobe would do that.

He has been known to even though he has confessed to not believing in God.