Other than Ash Ketchum himself, arguably the most enduring characters of the Pokémon anime are the Team Rocket trio of Jessie, James and Meowth. The villains were introduced all the way back in Pokémon's second-ever episode and have prominently appeared on a regular basis ever since, even as other main characters have rotated in and out over the years. In contrast, Jessie and James' foil characters, Cassidy and Butch, have actually been absent from the anime entirely for more than a decade.
As iconic as Jessie and James are, it's no secret that they're a far cry from what fans of the Pokémon video games think when they hear "Team Rocket." In the original games, Team Rocket was presented as a serious criminal syndicate that the people of the Kanto region were legitimately afraid of. Jessie and James, on the other hand, were often portrayed as incompetent -- albeit hilarious -- screwups who would get humiliated by Ash and his friends every other week.
However, Pokémon's 57th episode, "The Breeding Center Secret," revealed that the anime's version of Team Rocket may have been a force to be reckoned with after all and that Jessie and James might have just been outliers. That episode introduced Cassidy and Butch, two other members of Team Rocket who are basically Jessie and James' more competent counterparts.
It's clear right off the bat that the basic idea behind Cassidy and Butch was, "What if Jessie and James were actually good at their jobs?" It's established that Cassidy and Butch were star students at the Team Rocket academy. Not only that, but while Jessie and James would try and fail week in and week out to steal Ash's Pikachu, Cassidy and Butch were shown to have successfully stolen numerous Pokémon in their time.
The two Team Rocket squads also have rather similar designs, not to mention the exact same naming convention. Jessie and James' names are an obvious reference to the famous outlaw Jesse James. Meanwhile, Cassidy and Butch's names pay tribute to another notorious wild west outlaw, Butch Cassidy.
Their bitter rivalry was always palpable, with Jessie and Cassidy being especially disdainful of one another. In fact, Cassidy would frequently spread rumors that Jessie, James and Meowth were disliked by Team Rocket leader Giovanni and that the trio was in line for demotion.
Mind you, while Cassidy and Butch were certainly more competent than Jessie and James, they weren't exactly meant to be taken 100-percent seriously either. After all, the thing they're probably best remembered for is the running joke where Butch would get angry about people mispronouncing his name. Plus, while their capers had a higher success rate than Jessie and James', Cassidy and Butch could be just as bumbling as their rivals at times.
Still, right down to the color of their uniforms, Cassidy and Butch were always much more in line with what fans of the games had come to expect from Team Rocket. They weren't just one-off characters, either. Following their debut episode, the duo went on to appear in additional episodes of the original Pokémon anime, as well as follow-up series like Pokémon the Series: Ruby and Sapphire and the Pokémon Chronicles anthology.
Cassidy and Butch's final appearance to date came in "Sleight of Sand!" -- the 65th episode of Pokémon the Series: Diamond and Pearl and the 531st episode of Pokémon overall -- which aired in 2008 (January in Japan, July in the United States). There has been no mention of them ever since. But while Cassidy and Butch were written out of the show rather unceremoniously, their removal does make sense when you consider what exactly happened after Diamond and Pearl.
In Pokémon the Series: Black & White, the original trio of Jessie, James and Meowth turned over a new leaf. Often regarded as the series where Team Rocket got "serious," Black & White saw the comic relief baddies become far more credible as legitimate villains. During this period, their schemes were well thought out, well-executed and most importantly, more successful than ever before. Jessie and James were even given more video game-accurate black uniforms like the ones Cassidy and Butch always wore.
Simply put, now that Jessie and James had actually become good at their jobs, there was really nothing for Cassidy and Butch to play foil to anymore. At one point, Giovanni even referred to Jessie and James as his highest-ranking agents, which would imply that Cassidy and Butch had basically been forgotten about. In the end, Jessie and James had won.
However, their newfound competence didn't last. By the time Pokémon the Series: XY came around, Jessie, James and Meowth had mostly reverted back to their old, goofy selves. Even still, Cassidy and Butch have yet to resurface -- and it remains to be seen if we'll ever see the two grace our screens again.