Mark Alexander Knox, better known by his stage name Flex Alexander, is an actor, comedian, producer, writer, and dancer from the United States. His first TV role was on the 1993 ABC sitcom Where I Live, starring Doug E. Doug. Despite its critical praise, the series was discontinued the following year. 

Alexander then guest-starred in Sister, Sister, and The Cosby Mysteries before moving to Los Angeles in 1995 to pursue acting full time. The following year, he earned a lead part in another short-lived sitcom, Homeboys in Outer Space.

In 1997, Alexander co-starred in another short-lived series, Total Security, produced by Steven Bochco. Following the conclusion of Total Security, Alexander appeared in guest parts on Brooklyn South and The Parkers, and many films.

Alexander played Maya Wilkes' husband Darnell in the first season of the UPN sitcom Girlfriends from 2000 until 2001. Then, he left the show to star as Mark "Flex" Washington, a single parent on the UPN sitcom One on One,…