Warning: Spoilers for Dragon Ball Daima, episode #20
Dragon Ball Daimaset up an exciting possibility with the introduction of Join Bugs back in the beginning of the series, but the finale proceeded onward without ever putting the item to use. This bizarre decision may be one of the anime’s worst choices throughout its run, and there’s no clear reason as to why.
Back in episode #4, Goku found a variety of magical bugs, including the Join Bug, which was said toenable a new type of temporary fusion. Goku bought some of these Join Bugs, suggesting that he intended to use them in the future, or at least wanted to have the option. However, as the final battle rolled around, Goku lost his bag of bugs, and the bag wasn’t found again, so the Join Bugs that he’d purchased ultimately went unused. This left some fans quite a bit confused and let down by the series' ending, since the foreshadowed fusion never actually took place.

Why Would Daima Introduce New Fusions If Not To Use It?
Daima’s Failure to Use the Join Bugs Subverts a Basic Rule of Writing
In the world of fiction writing, there’s a term known as “Chekhov’s Gun,” referring to an object casually introduced in the story which must be used later on.Dragon Ball Daimahad several notable Chekhov’s Guns, with perhaps the most relevant being the eye on Hybis’s belt, which turned out to be the all-important Third Eye. Chekhov’s Gun is intended as a way to keep a story simple–if the item in question isn’t going to have an impact on the plot or characters, then why introduce it into the story at all?
The introduction of the Join Bugs without ever using them violates the idea of Chekhov’s Gun, something that’s generally a pretty big no-no in story writing. The Join Bugs are a particularly egregious case, since they immediately cause fans to think of other fusion methods used within the story,like Potara Earrings or the Fusion Dance. That gets viewers excited to see the Join Bugs pay off later on, but then it just doesn’t happen.Dragon Ballhas historically been written on the fly, so there often wasn’t much opportunity to foreshadow something Chekhov’s Gun-style, making it more notable when it does happen.

Dragon Ball Daima’s New Fusion May Have Been a Misdirect
The New Fusion Method Could’ve Been to Throw Off Fan Predictions
There is one other purpose for which an object might be introduced in the story, and that’s to mislead the audience or characters.This is generally known as a “red herring,” and refers to something that distracts from a more important plot point or story element.It’s possible thatDragon Ball Daima’s writers introduced the Join Bugs specifically as a red herring, to make fans think that the story would be resolved with a new fusion, only to surprise them by instead bringing out something unexpected–in this case, Super Saiyan 4.
Red herrings can be a bit dangerous to use in story writing, and are relatively rare outside of mystery-based stories. Misuse of red herrings can cause audiences to grow angry if used poorly, as they subvert their expectations. If the subversion ends up less interesting than executing it in the expected way, viewers will become displeased at this turn of events. Whether that’s the case withDragon Ball Daimaand Super Saiyan 4may be up to the individual viewers to decide, but it at least offers an explanation as to why Join Bugs were even mentioned at all.

Will Fans Ever See Join Bugs Pay Off?
Join Bugs Could Always Come Up Again Some Day
At present, it’s not clear ifDragon Ball Daimawill remain a limited series, or if it will be expanded with a second season at some point. If there does end up being a second season ofDaima, then it’s always possible that Join Bugs could play a role there. It’s even possible that Join Bugs could show up again inDragon Ball Super, now that they’re an established part of the universe. With the Demon Realm far more accessible than it was beforeDaima, it may be less of an issue to just pop over there and grab a few magic bugs.
It’s certainly a shame, from a fan’s perspective, that the Join Bugs went completely unused, as they held a lot of potential for interesting story developments.Dragon Ball Daimaabsolutely fumbled an easy win by not putting them to use, regardless of their intended purpose in the story.