Mr. Langhorne is a teacher at A Nigma High, who teaches Holger Holgaart and Lee Ping's first period class. It is unknown what subject he teaches, although the lab equipment in his room suggests either chemistry or general science.
He hosted a nature field trip in Fight or Flight.
In Revenge of the Cycle Killers, Lee and Biff begin to suspect he is a clone of Mark Twain.
- Mr. Langhorne has an uncanny resemblance to the American author and humorist, Samuel Langhorne Clemens, more commonly known as Mark Twain.
- Coincidentally (or perhaps not), Mr. Langhorne's last name references Mark Twain's real middle name, Langhorne.
- As seen in ____, he had a filmstrip which Lee routinely uses to go to the restroom from his class.
- It is eventually confirmed that he is indeed a clone of Mark Twain.