1. The show perhaps would not exist without 'Dick Tracy'.

 

At the start of the '90s, Van Dyke was 65 and viewed as being on the decline of his career. Warren Beatty cast the comedy veteran in a darker role for his colorful comic-strip flick, turning him into the crooked D.A. Fletcher. Van Dyke's wonderful performance would lead to him being considered for the role of Mark Sloan.

Image: Dick Van Dyke in Dick Tracy / Buena Vista Pictures

2. It was a spin-off of 'Jake and the Fatman' which was a spin-off of 'Matlock'.

 

Diagnosis remains one of the most successful spin-offs of a spin-off, even logging more seasons than Fatman's five. Andy Griffith would reprise his role of Matlock in the 1997 two-parter "Murder Two." We'll get more into guest appearances in a moment… 

Image: CBS

3. 'Diagnosis' created pilots for at least seven spin-offs, none of which were picked up.

 

Looking to return the favor, Diagnosis tried each season to spawn a spin-off with one or two nested pilots. This was at the behest of executive producer Fred Silverman. Some of the notable examples are "Sister Michael Wants You" in season one, which starred Delta Burke as a crime-solving nun, and "Retribution" in season five, a two-parter that featured Fred Dryer leading what would have been a new series called The Chief. Other nested pilots included Whistlers, about two vice detectives, and one with Leah Remini as a lawyer.

4. Seven other members of the Van Dyke family appeared on the show.

 

Diagnosis Murder was a family affair. Most obviously, Dick's son Barry Van Dyke (pictured) co-starred as Steve Sloan. Grandson Carey Van Dyke appears in a handful of episodes, as does his brother Shane. Oh, Barry's kids Wes and Taryn pop in, too. Jerry Van Dyke guests in an episode in season seven. Dick's daughter Stacy makes a rare appearance, as well.

Image: AP Photo / Mark Terrill

5. It featured main characters from classic TV shows like 'Mannix' and 'Mission: Impossible'.

 

There were far more guest actors beyond the Van Dyke name. Dozens upon dozens of them. What was nifty was Diagnosis' habit of bringing in TV veterans to reprise their famous roles. Mike Connors revived his character Mannix in season four, in what was a sequel to the Mannix episode "Little Girl Lost." Barbara Bain reprised her M:I role of Cinnamon Carter. Randolph Mantooth and Robert Fuller of Emergency! turned up in an episode about brushfires. It's a celebrity-spotting joy for fans of classic television.

6. It technically exists in the same fictional universe as 'Monk'.

 

Diagnosis proved so popular that it spawned a series of eight mystery novels. Characters from the second book, The Death Merchant, later reappeared in author Lee Goldberg's Monk novelizations. Hence, all these fictional sleuths are in the same shared universe!

Image: Amazon / Signet

7. Five Star Trek actors guest star in one episode, and Betty White plays Dick Van Dyke's sister in another.

 

Oh, back to more guest stars and family matters. Betty White shows up as Dora Sloan, Mark's sister. In addition, the episode "Alienated!" tickles lovers of 1960s sci-fi by roping in George Takei, Walter Koenig, Majel Barrett and Grace Lee Whitney from Star Trek (not to mention Wil Wheaton) alongside Bill Mumy of Lost in Space.