Just found this wonderful video on youtube, it features improvised dialogue from Dizzy Gillespie and George Mathews.

The Hole is a 1962 short animation by John Hubley and Faith Hubley that won an Academy Award for Short Subjects (Cartoons) in 1962.
The film uses improvised dialogue from Dizzy Gillespie and George Mathews as two construction workers at work in the bottom of a hole on a construction site discussing the possibility of an accidental nuclear weapons attack.

Above quote taken from wikipedia.