Mr. Huff is Greg's history teacher (during Rodrick Rules), who has only made one appearance so far in the book series, Rodrick Rules. He shares the same qualities as Mr. Litch - being authoritative and strict. Mr. Huff does not like Greg, and expects him to be as badly behaved as Rodrick even though that is only partially true.
He has a very big head, which appears to be bigger than Frank Heffley's.
In the online book, his name wasn't revealed and he was referred as "a teacher who had Rodrick in his class in middle school.".