There are two birthdates for Jack Black circulating on the internet: August 28, 1969 -- which seems more "respectable" sinced it is posted on impd and wikipedia-- and April 7, 1969, which is listed on yahoo and many other film sites.
The veritable astroldatabank does not weigh in with accurate birth information, so which sources do we trust?
Hmm.... The Aries Jack Black has all his personal planets in fire signs, which tend to be inspiring, exuberant, energetic. The Virgo Jack Black ... well, first of all, a Virgo Jack Black would be subservient and behind-the-scenes, not an in-your-face frontman for Tenacious D and all around crazy man. With Mercury in Libra, Virgo Jack Black would communicate in a graceful, people-pleasing manner, as opposed to Aries Jack Black, whose Mercury in Aries would speak impulsively and forcefully without a care for the feelings of others. (Think School of Rock.) I could go on....
However, there is a sensitive musician side to Jack, which is expressed by Virgo Jack's Moon in Pisces. Depending on the time of day Virgo Jack might have been born, his Moon could have been in a Grand Water Trine with Venus in late Cancer and Neptune in late Scorpio. Venus-Neptune aspects are famous for musicians, who express the ineffable (Neptune) through art (Venus). Additionally, an opposition from Pluto to his intuitive Pisces Moon would provide Virgo Jack the intensity and the drive to tap into the depths of the collective soul to ROCK OUT. On the other hand, the Aries Jack could have Pluto squaring his Sagittarius Moon, but would not have any significant Neptune aspects to his personal planets. (And unfortunately, without an exact birthtime we cannot know if any of these planets sit on one of his angles.)
I'm leaning towards Aries Jack, despite Virgo Jack's beautiful kite formation (Pisces Moon opposite Pluto, and trine Venus in Cancer and Neptune in Scorpio). I just don't see how Virgo Jack could channel the tremendous amount of energy that Aries Jack -- with all of his personal planets plus Saturn in fire signs -- conveys on screen and on stage.