Show Business: Stand-Up Comedy On a Roll

A thriving club scene primes stars of the future

It was a typical Sunday-night amateur show at the Improvisation comedy club in Los Angeles. Five minutes onstage for a blond dwarf who joked about her "white evening gowns made by Fruit of the Loom." Another five minutes for a purported Indian mystic called Ramogosh, who closed his act with a Sinatra- style rendition of I Did It Buddha's Way. After a parade of two dozen such neophytes, the audience of 200 was ready for some professional comedy -- and ecstatic when, at a quarter to 11, Jay Leno bounded onto the stage.

Leno, the lantern-jawed king of the stand-up circuit,...