This two-part story has been characterized as having "established the Joker as he is recognized today". In other words, this was a darkly murderous Joker with plans that could affect the whole of the world, rather than just an obnoxious two-bit hood with a taste for bad puns.
It follows in the style of Denny O'Neil's "The Joker's Five-Way Revenge", which brought the Joker back into comics after an absence of some years. Like O'Neil's earlier work, "The Laughing Fish" sought to define the Joker as Batman's greatest enemy, by showing Batman's serious logic as the natural counterpoint to the Joker's random lunacy. This relationship had not been the norm for Batman comics of the 1950s and 1960s. Englehart's work to cement the characterization begun by O'Neill is thus a milestone for the Joker character, even if modern readers might not be able to see this story as particularly exceptional today.
This story was later adapted for television by Paul Dini, and released as episode 33 of Batman: The Animated Series (1992).