When David McCullough (writer) met Paul Giamatti for the first time out of character, he did not recognize him as the actor who played John Adams

Goofs

Episode 5 shows John Adams brushing his teeth with a toothbrush - this is not incorrect, although toothbrushing was not the most common form of dental hygiene at the time. Most people, especially the poor, would have rubbed their teeth with a rag and salt or ashes. Tooth brushes were in use in China c. 1400, in England about 1690, and mass produced tooth brushes were available in the 1780s. The modern American toothbrush was invented in 1938. See more