Virgo resides on the cusp of David's 10th house of profession. The placement of its ruler, Mercury, describes David's career. It's in Pisces, the sign representing nighttime and in the 4th house of home. David is invited into the homes of America every night. Still, it's a powerful planet in David's horoscope.
Mercury governs the mind, intellect, and all forms of communication.
When peregrine, all things are considered from the viewpoint of an outsider. From this perspective, David is able to find the ridiculous element in common, everyday events and activities. His natural talent for show business is shown by the placement of his Aries Sun in his 5th house of creativity. David Letterman is a household name. Another plus for his comedic talent is Mercury in Pisces.