What effect did Pokemon have on the metagame?
Thwackey was an alright pivot and wallbreaker in the early SS ZU metagame when it only had Overgrow, but it only could have one of good power, bulk, or speed depending on the one item you could choose. Despite having Knock Off, Thwackey's poor stats made it overshadowed by greater offensive pivots like the very potent Silvally-Grass. Grookey then received its Hidden Ability, Grassy Surge, in an early June 2020 Pokemon HOME update. Grassy Surge Thwackey was not the god you know today just yet without Grassy Glide, but it was far better than before. Thwackey's Wood Hammer now had the oomph to make it a natural wallbreaker, and its previous tools of U-Turn and Knock Off synergized with its terrain setting. Cufant was a huge beneficiary of Grassy Terrain, which boosted its Power Whip, provided passive recovery on what was one of our only bulky Steel types, and gave Cufant a way to play around Earthquakes from Ground types like Mudbray and Hippopotas. All of this is to build up to Thwackey receiving Grassy Glide with the release of the Isle of Armor DLC, leading to it being put on a slate and unanimously quickbanned from ZU on June 28th 2020.
But behind every monkey is always a smaller, littler, cuter monkey.
I'd like to say that Grookey rose to try and fill the Thwackey-shaped hole in DLC1 ZU, but the speed and bulk and power problems Thwackey had when it was running Overgrow were even more pronounced in Grookey. Gourgeist-Large was one of the most premiere Pokemon in ZU during the July metagame, and it stuffed Grookey. Gourgeist-Large could pair with Grookey on Grassy Terrain teams, but the playstyle was seen as niche during this metagame. Grassy Surge was nice for supporting Pokemon like Cufant, Torracat, and Trubbish just as it had been, but Grookey was a relatively slow and frail pivot. Even with Grassy Surge + Grassy Glide, Grookey did not carve itself into ZU until August 2020.
August 2020 brought a very large tier shift for the ZU tier, and even bigger for Grookey. Musharna, Beheeyem, Trevenant, and Swoobat were all amazing candidates for Grassy Terrain teams. Grookey became less of dead-weight on teams and more of the stinger to Grass, Psychic, and Ghost spam archetypes, which warped the metagame.
A unanimous ban of Musharna in the middle of August did not curb the Grassy Terrain archetype enough, and a second slate was developed in late August. The determination of what was truly the root of the problem was messy, with some considering this to be either Trevenant (one of the strongest wallbreakers on Grassy Terrain teams) or Grassy Surge (as Grookey was unproblematic without the ability in the way Politoed would later be without Drizzle). Grookey and Swoobat (which had survived the previous slate on a perfect 50-50 vote) were tested on the same slate, where Grookey remained ZU with a 50-50 split and Swoobat became Swooban unanimously.
Grookey and Grassy Terrain teams remained in good standing for the rest of the DLC1 metagame. With "only" Beheeyem, Trevenant, and Gourgeist-Large, Grassy Terrain teams were strong but matchup-reliant leading to the release of the Crown Tundra.
The effect of the Crown Tundra was immediate in ZU, introducing Combusken and Golbat as significant checks to the archetype and Grookey itself. Combusken was quickbanned before the first November 2020 tier shift, which also took Golbat away. However, a huge amount of Pokemon from PU were flushed into ZU in the same shift, and Trevenant rose to NU with Golbat.
In the first November metagame, Grookey was more reactionary than dominant, as it was responding to a surge in Rain teams which its own archetype had an intuitively good matchup against. A number of the new drops were challenging to the Grassy Terrain archetype, such as Bouffalant, Mawile, and Gourgeist-Small. In the same shift though, Rapidash-Galar came down and picked up where Musharna and Swoobat had left off as a Psychic-type sweeper on Grassy Terrain teams. Musharna itself was even unbanned right after tier shifts, giving Grassy Terrain its mojo again.
Grookey became controversial again as the second November tier shift brought a number of metagame-warping Pokemon, which was something that had already happened twice in less than a month. Pincurchin and its Electric Surge returned and challenged Grookey as both a terrain setter and the face of terrain archetypes. Grookey could provide its team with strong Grass-type support against Rain, had greater positioning than Pincurchin thanks to U-Turn, and packed Knock Off and priority to boot. Pincurchin boasted hazards with Spikes and a great matchup against Defoggers, reliable recovery, and the ability to take a hit if necessary. Trevenant and Leafeon both dropped back into ZU at the same time, giving more potential abusers to work with. Gourgeist-Small rose to PU during this time, which took away another easy check to Grassy Terrain, Rain, and Electric terrain teams.
December 2020's first tier shift was smaller, dropping multiple good to decent checks to Grassy Terrain teams like Avalugg, Pinsir, and Ninetales. Gourgeist-Small returned to ZU, and Trevenant rose up to PU to take its place. Despite Grassy Terrain growing more powerful, the state of the metagame with its matchup fishing and specifically the threat of Rain HO prompted a ban of Drednaw in early December. Terrain teams were discussed more seriously during this time, with concerns over how to properly decide and deal with whatever source of the teams' power once again. Psychic types with their respective Seeds, Grookey or Pincurchin themselves, or Electric/Grassy Surge were discussed as potential issues.
The second tier shift of December 2020 dropped Drifblim into the metagame, giving Grookey and Pincurchin another playmate. Distaste for the HO archetype matchup nature of the metagame was expressed by some players, but little action happened to address it. Rain was no longer as overbearing, giving Grookey and Grassy Terrain teams a worse overall matchup in the fish. However, new HO playstyles like Trick Room featuring Pokemon like Marowak emerged, giving Grookey new prey.
January 2021's tier shift completely changed ZU, but for Grookey, the biggest part was that Thwackey dropped. With its adolescent self back in ZU, Grookey was finally able to retire.
In what main roles was Pokemon used?
Grookey, with Grassy Surge, was most potently used as a setter of Grassy Terrain on the aptly-named Grassy Terrain offense Archetype. Grookey itself could hold a Terrain Extender to support its teammates with more turns, or a Choice Band to abuse its own terrain with a stronger Grassy Glide.
What caused it to have a significant impact?
Grassy Surge was the selling point of Grookey. Grookey was rarely used on its own as a wallbreaker, pivot, revenge killer, or cleaner in the way that Thwackey was and is today. The power of friendship helped Grookey's breakout success, as it needed strong abusers of its terrain like Musharna, Rapidash-Galar, Beheeyem, Trevenant, and Gourgeist-Large in order to be an operational head of the archetype. A number of bans disrupted its initial success, but Grookey would lead Grassy Terrain teams through the chaotic period between the release of the Crown Tundra to January 2021. The increasingly offensive and matchup-based nature of the metagame benefitted Grookey's playstyle, and Grassy Terrain had a naturally good type matchup against other popular playstyles like Rain and Electric Terrain.
How do/did you deal with this Pokemon in ZU?
Grookey was rarely the element of Grassy Terrain teams that a player was aiming to check. Grookey hardly had the bulk to be using CB Wood Hammer in Grassy Terrain, much less take a hit, so positioning yourself to not allow Grookey in on a passive Pokemon was important for balance teams. Offensive teams could use faster Pokemon which resisted Grass like Gourgeist-Small, Ninetales, or Emolga depending on your metagame to disrupt and revenge kill Grassy Terrain abusers. Grookey's Knock Off was useful, but did not synergize well with Poltergeist on Trevenant or Gourgeists, so there was an amount of in-game counterplay based around item control. Item selection in the teambuilder with choices like No Item on bulky Pokemon like Musharna, Gourgeist-Large, and Leafeon reflected the pressure Grassy Terrain teams could put on, as well as their linearity in builds. Grassy Terrain teams often featured Grookey, one or two Grass type Grassy Glide abuser, one or two Grassy Seed sweepers, and a couple of support Pokemon which compressed hazard setting roles or could cover the teams' weaknesses. Carkol, Mareanie, Mawile, Stonjourner, Wartortle, and Whirlipede were among some of Grookey's teammates at various phases of the metagame, so checking Grookey's support was different in every meta. Dark types which also resisted Grass like Pawniard, Zweilous, and Vullaby were often helpful blanket checks to many Grassy Terrain Pokemon, but they flagged against Galarian Rapidash's Fairy STAB and were threatened by Musharna's Moonblast. Bouffalant provided teams with a unique Grass immunity at the same time as a Ghost immunity. One of the best ways to beat Grassy Terrain in the late 2020 metagame was simply not to run linear offensive archetypes, as Grookey's Grassy Terrain teams naturally had good matchups against Rain, Electric Terrain, Trick Room, and webs. Grass types, especially itemless ones, were very effective at taking advantage of common Grassy Terrain abusers; Leafeon, Gourgeist-Small, Gourgeist-Large, Lurantis, Bellossom, and Lilligant all often found openings against choice-locked or poorly positioned abusers like Trevenant/Gourgeist-Large or Grookey itself to set themselves up or support their teams.
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