Not surprisingly, the first film's Mrs. Clouseau is conveniently forgotten, but we are introduced to a few more secondary characters: Kato, Clouseau's karate-chop-throwing valet; Clouseau's assistant, the amusingly named Hercule; and Dreyfus, Clouseau's superior, pushed to his limits and beyond by the strain of dealing with Clouseau's idiocy. All the characters are presented in the same just-barely-over-the-top style, which ends up working quite well. (The disappearance of Madame Clouseau is actually more incidental than deliberate: A Shot in the Dark is an adaptation of a stage play, and wasn't originally related in any way to The Pink Panther until Blake Edwards decided that the character of Inspector Clouseau would work well as the protagonist. And the rest is film history.)
The opening scene is surprisingly poorly done, but fortunately it's not typical of the film as a whole. The film opens with a long scene with various people sneaking around from room to room in large house, which in itself is a fine opening, except that it drags on long enough that you might start thinking that you're supposed to actually know who these people are, or to keep track of what they're doing. It probably does make the film more entertaining if you manage to retain some of this, but at least it's not at all necessary to enjoy the story. Just about when I was losing my patience with the scene, the film cuts to the amusing animated (but panther-free) opening credits, and from then on the story moves smoothly onward.
All in all, A Shot in the Dark is a better film than The Pink Panther. It's more evenly paced, and the comedic focus stays clear throughout the film, giving Sellers ample room to expand the character of Clouseau. Though it doesn't have the moments of pure comic brilliance that shine through The Pink Panther, the humor in A Shot in the Dark is more consistent, and certainly has quite a few very amusing moments.