In Chomp!! Defeat Drednaw, while traveling, the group's truck accidentally ran over a group of Drednaw, resulting in a flat tire. While trying to find the cause of it, the Drednaw attacked. Scorbunny was able to distract two of them, though one chomped down on Grookey's stick. Grookey refused to let go, resulting in a tug of war. Grookey eventually won when another Drednaw charged into the one holding Grookey's stick, allowing the Chimp Pokémon to knock them both out.
In Zap!! A Rising Beam of Light, Henry decided to give his team nicknames in order to distinguish them from other Pokémon of the same species. Choosing to name them after the gear they used, Grookey was called Twiggy. Later during the day, a pair of Team Yell Grunts tried to destroy the new uniforms that Henry and Casey received. While Lancelot and Scorbunny distracted them, Twiggy snuck behind the fight and directly attacked the Grunts, driving them towards a Pokémon Den. This allowed his Trainer to push the Grunts into it and force them into a Max Raid Battle against a wild Gurdurr.
Twiggy battling Nessa's Drednaw
In Toasty!! Battle Against Toxapex, to prepare for his gym battle against Nessa, Henry used Twiggy to battle against Marvin and Sniffler, where they practiced Twiggy's strategy of drumming its stick off the ground to agitate his opponent. Sniffler responding by using its tears to become invisible, though Twiggy countered it with a Branch Poke and won. After the battle, Twiggy evolved into Thwackey. Henry later used Twiggy as his first Pokémon against Nessa and her Toxapex. Twiggy started the battle by drumming his branches on the ground but quickly became frustrated when Toxapex was unaffected by the noise. Twiggy then attacked the Brutal Star Pokémon directly and was poisoned by Toxapex's Baneful Bunker. Realizing that temperature had something to do with how Toxapex protected itself, Henry had Twiggy use Sunny Day, opening up Toxapex and allowing Twiggy to defeat the Brutal Star Pokémon. Nessa then sent out her Drednaw, which she immediately Gigantamaxed.
Due to its large size, Gigantamax Drednaw easily overwhelmed Twiggy with its Max Moves. Henry countered by Dynamaxing Twiggy, determined to win the fight with only him. The two exchanged a few blows, though Twiggy's speed wasn't enough to match the Bite Pokémon's defense. He finally managed to land the finishing blow when Drednaw extended its neck out to bite Twiggy, earning them the victory.
In PASS11, Twiggy was one of the three Pokémon Henry brought to use in his gym battle against Kabu.
In PASS19, Twiggy, under Casey's command, joined Raboot and Sniffler to defeat Gordie's Stonjourner. Twiggy used Branch Poke on the ground to create holes for Sniffler to fill with Water Gun, soaking the Big Rock Pokémon. Afterward, Henry tried to get Twiggy to stop a herd of Eiscue from stealing Melony's Mr. Rime, but they froze him solid and knocked him out.
Personality and characteristics
Twiggy protecting his stick
Twiggy is an upbeat Pokémon, often seen smiling and excited at the idea of battling. He is very protective of his stick, refusing to give it up even in the face of danger. Using its sticks, Twiggy is able to beat them off the ground to create a rhythmic drumming that can agitate opponents. After evolving into a Thwackey, Twiggy is shown to get irritated when things don't go his way.