After starting his career in theatre, Mark Blum appeared in a number of hit films during the mid-'80s, many of which were written or directed by top names in the comedy field. He made his big-screen debut with a small role in "Lovesick", the 1983 Dudley Moore vehicle by "Annie Hall" co-writer Marshall Brickman. This was shortly followed by "Desperately Seeking Susan", in which he played Gary Glass, the husband of a discontented suburban housewife (played by Rosanna Arquette) who becomes obsessed with a woman who leaves messages in the personal ads section of a newspaper; and ""Crocodile" Dundee", wherein he played the title character's romantic rival. During this time, Blum also appeared in the decidedly non-comedic '88 thriller "The Presidio" as a villain, a wealthy man somehow connected to a shooting at an Army base. In '87, he costarred on a television sitcom for the first time, but the resulting "Sweet Surrender" was quickly canceled, as was his 1990 series "Capital News", which centered around a Washington, D.C. newspaper. However, Blum was no stranger to television and movie audiences during the '90s and 2000s, guest starring in everything from crime dramas to comedies.