Kreppel started his acting career by starring in the improvisational theater group, "The Proposition," which included Jane Curtin, Josh Mostel, Judith Kahan, and Munson Hicks.

When the group moved to New York, Kreppel began starring in off-Broadway plays, including Godspell and Tuscaloosa's Calling Me...

While appearing at the New York Shakespeare Festival, he notably starred with Meryl Streep in the musical, Alice in Concert, by Elizabeth Swados.

[2] In 1979, Kreppel moved to Los Angeles to become the memorable waitress-harassing pianist, Sonny Mann, of It's a Living.

Among other projects, Kreppel directed and produced with his partner in WetRock Entertainment, Ms. Murphy Cross, Jay Johnson: The Two and Only, for which he won a 2007 Tony Award for best special theatrical event.