What song did HAL sing as Dave deactivated him in 2001?
The song was "Bicycle Built for Two" (a.k.a. "Daisy, Daisy"). This song was the very first tune played on a computer, at Bell Labs in the 1950's. The implication was that HAL was "devolving."
Random Trivia Question:
We never learn the Mule's name, but he took this title during his reign.