Jamil Walker Smith

With a voice and face that should be familiar to children's TV fans and sci-fi aficionados alike, Jamil Walker Smith began as a voice actor on the hit Nickelodeon show "Hey Arnold!" After a number of years, he rose to fame as Ronald Greer on "SGU Stargate Universe."

After launching his career as a teen actor on mid-1990s sitcoms and dramas, including a meaty role in "Fresh Bones," a Haitian voodoo-themed episode of "The X-Files," he played the role of Mike on ABC's African-American family sitcom "Sister, Sister" in 1996. That same year, he launched his voice-over career with the part of Gerald Johanssen, the title character's best friend on "Hey Arnold!," a Nickelodeon's kids' comedy set in an inner-city multi-ethnic boarding house.

The show was a massive success, running for five full seasons and spawning "Hey Arnold! The Movie" in 2002. Throughout the show's run, and after it ended in 2003, Smith was at no loss for work; he'd matured into a handsome young man.

After writing, directing, and starring in the short "The Son" in 2007, he played roles on prime-time mystery dramas including "Medium" and "Cold Case." He later had a co-starring part on the hit sci-fi drama "SGU Stargate Universe," as Master Sgt. Ronald Greer.