From another discussion group: Natalie and Sharona's similarities.
Just some cut and paste stuff (disclaimer, 99.99+ are my own observations, but the thread came from another group.)
Natalie & Sharona love their children and would do anything for them.
Natalie & Sharona love Monk. It's the reason they stay(ed).
Natalie & Sharona held several jobs before working for Monk
Monk has rescued Natalie & Sharona (Usually though some phobia)
Natalie & Sharona has quit her job with Monk only to return (except for the time Sharona didn't - though technically, she didn't 'quit', she just left.)
Natalie has killed a man/Sharona might be capable of killing a man.
Natalie & Sharona didn't get paid enough (but Sharona was paid more than Natalie, and Natalie was paid for her expenses)
Natalie's money phrase "Ka-ching!"/Sharona's money phrase "No Backsies!"
Natalie hugged Monk after thinking he was dead (on the Run)/Sharona hugged Monk after thinking he was dead (Mexico)
Natalie & Sharona went to the theater with Monk to watch her family member on stage (Critic/Theater)
Natalie & Sharona tried to get Monk to be more assertive about being paid (Big Reward/Billionaire Mugger)
Natalie & Sharona came into Monk's life just when he needed her.
They are both feisty, but I would say Natalie is more spunky, and Sharona is more sassy.
They are both writers. Sharona had her murder plagiarized (Wolf) and Natalie writes the Monk novels under the pen names Lee Goldberg and Hy Conrad.
They both kissed Monk: Natalie - lots of kisses on the face (On the Run II), Sharona, one brief one on the lips (Get's Married).
They both had a bit of a wild past. Natalie called herself a wild child a couple of times, and in Mr. Monk's Favorite Show, she and Randy were talking about the book and she said something like ,"This is filthy, and I thought I was a wild child." (Favorite Show) and Sharona, according to her mother "S.T.O.L.E. a car." (Theater)
They both believe in occult-y things: Natalie believed in voodoo,(Voodoo Curse) Sharona believed in psychics. (Psychic)
They were both in long distance relationships in season 8. Natalie with Albright and Sharona with Disher. (Bonus - both their LDR's are Lieutenants)
They both have been known to drive other people's NEW CARS like CRAZY! Sharona: Monk's new red (mustang?) in (Medicine), Natalie: The Captain's new car in (Three Julies).
They both served turkey dinners to homeless individuals. (Missing Granny/ Miracle) (Bonus, Monk obsesses over Bum Gravy in both)
In a still image from Mr. Monk and Sharona, you can spot a small tattoo of the Star of David on Bitty Schram's ankle, so they both have tattoos.(Mr. Monk is at Your Service)
Monk sent both women flowers
Circus (Blank Card - he didn't know what to say)
Rapper (Happy Secretary's Day!)
They both kind of rejected them.
Monk fiddled with their clothes in "inappropriate" ways.
He uncovers the jacket on Sharona's shoulder in Theater
He fiddles with Natalie's blouse in Drunk
They both admired Monk in his uniform, Sharona in Carnival and Natalie in Bank.
They both encountered naked individuals on a case: Sharona - Baseball, Natalie - Naked Man
The both "wore" a piece of Trudy's jewelry Sharona - Trudy's wedding Ring in Gets Married Natalie - Trudy's diamond bracelet in Bank. (Bonus: Both were trapped in at least one scene while wearing the jewelry)
They were both the bad guy tell. He was "the guy" if Sharona liked him, and if Natalie hated him.
Monk fake explained baseball to Benjy for Sharona. (Baseball)
Monk fake explained relationships to Julie for Natalie. (Birds and Bees)
They both encouraged Monk to date; Sharona in Blackout & Natalie in Falls in Love.