- Clark has a "Bacon Number" of 2.
He was in On Their Knees with Maury Chaykin,
Maury was in Where the Truth Lies with Kevin Bacon.
- He spent time performing improv with Toronto's Second City troupe.
- Johnson gained his cop attitude after studying Sonny Grasso. Grasso, a real cop, had been played in the film The French Connection by Roy Scheider.
- As a child actor, he toured in productions of musicals such as Finian’s Rainbow and Porgy and Bess.
- During a short career in football he was cut by Buffalo twice, Pittsburgh once, and one season the Canadian Football League paid him $250 a week for him to stay home.
- While on summer break between seasons 4 and 5 of Homicide: Life on the Street, Clark went back to Canada and assisted an film rigging a special effects blast.
- While working an explosion on the film The Dead Zone, he received 38 stitches on his arm after being cut with broken glass.
- He is the father of two girls: Cassandra Johnson (born in 1983) and Michaela Johnson (born in 1985.) Both daughters were from his first marriage.
- Clark Johnson married his second wife, Heather Salmon, on November 26, 1994. They met in Toronto during the summer of 1993 at an aerobics class.
- In 2006 Clark Johnson was nominated for a Black Reel Award for his direction of the film The Sentinel.
- Detective Meldrick Lewis, the character Clark Johnson played on Homicide: Life on the Street, is the only regular cast member to have been with the show all seven seasons and the reunion movie to remain a Baltimore homicide detective.
- He was nominated for an Emmy in 2002 for Outstanding Direction for a Drama series. The nomination honored his direction of the pilot episode of The Shield.
- His supporting performance in the film Rude was nominated for a 1996 Genie award.
- His guest performance in the series E.N.G. earned him a Gemini Award nomination in 1995.
- In 1999 he was nominated for an Image award for outstanding supporting actor in a drama series for his role as Detective Meldrick Lewis in Homicide: Life on The Street.
- Acting seems to run in his family. He is the younger brother of Taborah Johnson, who is an actress.
- Jazz singer Molly Johnson is his sister.
- Clark Johnson: (Talking about his character Meldrick Lewis) I wanted to make this guy like Everyman. When he gets heartburn from eating a meatball sub at 2 a.m., I want cops to go, 'Oh yeah, I know that feeling.'
- Clark Johnson: The character of Meldrick just sort of evolved as we went along. I would say that he's 50 percent from me and 50 percent from the writers. Now, if you talk to these arrogant writers, they'd probably say 60/40 on their part, or even 70/30, but you know how writers are.
- Clark Johnson: If I went back to special effects it wouldn't bother me, I don't want to go on Hollywood Squares to pay the rent.
- Clark Johnson: I'm not a big fan of actor-directors.
