Team Yell was formed when Pier's younger sister Marnie registered for the Gym Challenge, several Gym Trainers from the Spikemuth Gym banded together to form Team Yell and act as a cheering gang for her, but also became vandals attempting to takedown Marnie's competition. Team Yell first appears in Motosuke. The trainer is forced to fight them before Marnie arrives and dismisses them. Team Yell then later appears in various cities and towns, often blocking the trainer from advancing until they earn the town's gym badge.
Other instances in which the trainer is forced to fight them includes: Immediately outside the Hammerlocke west exit and Galar Mine 2. Most notably, they blockaded the main entrance to Spikemuth in an effort to prevent trainers from advancing in the gym challenge so that Marnie would be the only one to reach the finals.
After the player character defeated Piers it was revealed that the Team Yell grunts are the trainers that make up Spikemuth's gym trainers, and their overzealous behavior was because of Spikemuth's continously deteriorating state as less and less people were visiting the town due to it's lack of a Power Spot. Spikemuth's Trainers were afraid that their Gym would be shut down and the town would lose one of its last fame and revenue streams, so they formed Team Yell to help Marnie become the new champion which in turn would bring more people to Spikemuth. With that revelation, Piers and Marnie instructed Team Yell to open up the gates to Spikemuth and stop trying to boycott other trainers, allowing the Gym Challenge to continue as intended.
During the Championship Finals Piers had Team Yell assist the Trainer in finding the League Staff member who held the key to the monorail and later helped the Trainer and Hop sneak into Rose Tower. During the post game Team Yell returned to their duties as Gym Trainers in Spikemuth, which now has more tourists visiting it as Marnie became popular during the Gym Challenge and she is the new Gym Leader. Several members can also be seen outside the Wyndon Stadium, now claiming that they just want to watch Battles and will no longer cause trouble.
- Team Yell can be considered as a representation of toxic fan-bases in reality.
- Their behavior might also be inspired by football/soccer hooligans who support one team and get into fights with fans of opposing teams.
- In keeping with Piers' and Marnie's rock musician theming, their attire could also be a reference to punk music as a genre.
- The badges worn by male Team Yell grunts look similar to a single Klink with sharp ridges.
- The two-pronged, noisemaking device male grunts carry resemble vuvuzelas, a noise making contracting used by zealous fanatics that are frequently banned from being brought into stadiums due to how disruptive they are.
- Much like Team Skull before them, Team Yell is yet another group to not be a proper criminal organization. However, Team Yell is also similar for all the Grunts respecting a single person.
- The symbol of Team Yell is shared with Piers, the Dark-type Gym Leader. This symbol can be seen outside the Motostoke Stadium, foreshadowing that Team Yell is composed of Spikemuth Gym Trainers.
- They are the second villainous team to have a Gym Leader as a leader, after Team Rocket.
- Unlike the other villainous teams, however, Team Yell's leader does not appear to be actively directing their actions, nor does he seem to even be aware of them, as evidenced that at first he thought no one wanted to challenge him because of his bad reputation and did not know Team Yell blocked the entrance to the city. Thus, Team Yell itself is not exactly a villainous team, and is instead being an anti-hero team because of their leader is not villanous either. Piers does however take command of Team Yell after he's defeated by the player character.
- Team Yell is the first antagonist team that isn't disbanded after their defeat, and in fact they actively become allies to the player character aftewards.
- It can also be argued that Team Yell is the first antagonistic team to indirectly succeed at their goals, as even though Marnie did not become the new champion her performance at the Gym Challenge did win Spikemuth enough publicity to attract more tourists.