Basically, the 5 films involving Peter Sellers:
The Pink Panther (1963) - A comedy crime caper involving Sir Charles Lytton (The Phantom), a bunch of other characters, and the dumb Insp. Jacques Clouseau, who is attempting to catch the Phantom and stop the theft of the Pink Panther diamond. Audiences loved Inspector Clouseau's character leading to further films with him as the central character.
A Shot in the Dark (1964) - Inspector Clouseau takes the central role in the who-done-it comedy. The film introduces many of the key characters including Clouseau's servant Cato and boss Charles Dreyfus. Dreyfus knows that Clouseau is an idiot, who manages to solve cases through dumb luck. He is mentally impacted by Clouseau and wants to kill him.
The Return of the Pink Panther (1975) - The famous Pink Panther diamond is stolen again with clues pointing to the Phantom, who must investigate to clear his name. Inspector Clouseau undertakes the investigation in his dumb manner in a different direction. However, as usual, luck smiles on Clouseau as he happen to be in the right place at the right time to unintentionally solve the case. Clouseau is hailed as a hero. Chief Dreyfus is finally thrown into mental asylum.
The Pink Panther Strikes Again (1976) - Dreyfus has recovered, is happy, and about to leave the mental asylum. But on the fateful day, an unfortunate encounter with Clouseau relapses his mental condition and is locked up again. Dreyfus escapes the asylum and directly/indirectly hires assassins to kill Clouseau.
The Revenge of the Pink Panther (1978) - The mafia is unsure if Clouseau is a genius or an idiot but in any case wants him eliminated as he has interfered enough in its matters. A lucky breaks ensures Clouseau survives an assassination attempt but remains dead for convenience to investigate. Dreyfus is finally out of the asylum and gets the job of the chief back. Clouseau meets Dreyfus, but he can't tell others that Clouseau is alive for the fear of him being seen as imagining things and sent back to the asylum. Dreyfus also has to make a speech to praise Clouseau, which he struggles to deliver knowing there is nothing to praise the idiotic but lucky Clouseau.
No need to say that each film has something in it to make you laugh out loud. I am planning to rewatch these. Which one is your favorite?
Below, the famous dentist scene b/w Dreyfus and Clouseau in disguise in The Pink Panther Strikes Again: