The FBI assigned a team to Sacha Baron Cohen during the filming of the movie due to numerous reports of a "Middle eastern man traveling the Midwest in an ice cream truck."
Borat is based on a Russian doctor Sacha Baron Cohen once met. He said the doctor was completely hilarious, but it was unintentional.
When Borat Sagdiyev (Sacha Baron Cohen) speaks Kazakh, it is mostly Hebrew disguised by a heavy fake Eastern European accent. The Hebrew is quite understandable and contains many in-jokes. Baron Cohen admitted this in a rare "out of character" radio interview on National Public Radio in the United States.
Johnny Depp, George Clooney and Steve Martin, all of whom are huge fans of Sacha Baron Cohen, contacted him about having a cameo in the movie. However, Baron Cohen refused because it would have ruined some of the gags if they knew what was going on.