Mr. Langley is a character who is referenced but not depicted in the film version of 2001: A Space Odyssey. The HAL 9000 computer's reboot speech begins with the following line:
Good afternoon, gentlemen. I am a HAL 9000 computer. I became operational at the H.A.L. plant in Urbana, Illinois on the 12th of January 1992. My instructor was Mr. Langley, and he taught me to sing a song.
In the novels 2001 and 2010: Odyssey Two, as well as the latter's film adaptation 2010: The Year We Make Contact, HAL's "birth" is reassigned to 1997. Its education is credited to Dr. Chandra, and Langley is never mentioned again. Implicitly, Arthur C. Clarke retconned Langley into Chandra.
Notably, Langley, Virginia is the common appellation of the location of the official and public headquarters for CIA, NSA and NRO.