The Mentalist was a more serious version of Monk. I think that the connection between Psych and The Mentalist is tenuous (despite the references in Psych). As for the connection between Monk and The Mentalist, here are the character comparisons…
Patrick = Monk (the main man loses his wife to a killer who takes seasons to be caught*).
Cho = Leyland (the straight-faced detective).
Rigsby = Randy (the dim-witted sidekick).
Lisbon = Natalie (the main assistant).
Van Pelt = Sharona (the lesser assistant who eventually dates the dim-witted sidekick).
Both TV serials have an episode involving a parachute blunder. Both serials have an episode where the detective is blind. I won’t tell you which episodes because it would spoil the surprise. Still, fans of The Mentalist can hardly say that the blind connection was a coincidence. As for the M connection, these serials are the ultimate murder mysteries whose content is embodied by the M in the titles.
The makers of Psych seem to think that The Mentalist is an imitation. However, The Mentalist was about someone who previously pretended to be psychic. To the credit of those behind Psych, The Mentalist also had an episode about an Old West tourist attraction. What separated Psych from these other serials is that it avoided the gimmick of having the main goal of the protagonist be the sub-plot of almost every episode.
As for similarities between Psych and Monk, there are episodes about retirement homes, fake aliens, daredevils and murdered models. After Psych came to an end, people wished that there could be a TV movie which allows for a Monk crossover.
Psych isn’t all that original, either. It seems to have been inspired by the scene in Beverly Hills Cop II where Eddie Murphy’s Axel Foley pretends to be psychic in order to hide the fact that he is a detective.
As for the above photo, Psych and Monk have episodes about murdered food critics. Here are the number of times that I laughed throughout binge-watching both shows….
I asked Kelly Metzger about the remnant of a deleted scene that can still be seen in an episode of Psych titled Not Even Close…Encounters. She said: “Oh, I ran up to the main black guy and asked him if he was LeVar Burton. But when I watched the show, it looked like that little moment was cut.”
* Intriguingly, this is the same premise as Life and Endgame.