Pokemon Sword and Shield's Sinistea and Polteageist put a Ghost-type spin on Beauty and the Beast's talking tableware, but raising the little Chips into Mrs. Potts requires dedication and luck - especially when trying to make sure a particular Sinistea isn't counterfeit. Yes, like many of Sword and Shield's more unique Pokemon, catching and evolving Sinistea is rather complicated.
Sinistea is far from the first Pokemon with mutliple forms or complicated evolution requirements. Sword and Shield's Gigantamax Pokemon are special versions of regular Pokemon that change form when Dynamaxed, meaning not just any old Drednaw can Gigantamax, despite the Gigantamax Drednaws looking identical to the normal ones when not yet Dynamaxed. On top of this, evolving Pokemon like Galarian Yamask - as well as Alcremie, which also comes in a Gigantamax-capable variant - can get extremely complex, requiring the use of version-exclusive items, the knowledge of certain moves, or even the purposeful damaging of a Pokemon. It can be a lot to wrap one's mind around without a guide, especially since few of these methods are directly stated in-game.
Sinistea has both an obscure second form and a unique evolution method, both of which are intertwined. Because Sinistea and Polteageist are is the spirits possessing the teaware and not the teaware themselves, the teacup and tea pot they occupy come in both "authentic" and "counterfeit" varieties. Like Alcremie's many evolution forms, any given Sinistea's form has no effect on gameplay, so the only trainers that need to bother with catching the authentic form are those who care about this subtle difference: Authentic Sinistea and Polteigeist have a tiny stamp/seal printed on the bottom of their teaware. Authentic Sinistea are extremely rare, especially because Sinistea can only be caught through random encounters in Glimwood Tangle (the fairy forest north of Stow-on-Side). Even if a trainer does catch an authentic Sinistea, the seal can be nearly impossible to see in most circumstances. The easiest way to distinguish the two is through Sinistea's evolution method.
In order to evolve Sinistea, players need either the Chipped Pot or the Cracked Pot item. A free Cracked Pot can be found on a Stow-on-Side rooftop (accessed via the ladder to the right of the path leading to the town's version-exclusive Fighting or Ghost gym), but the Chipped Pot can be obtained from the bargain vendor's shop in the main Stow-on-Side street. The vendor's stock rotates daily, so players will have to check back often to see if he's selling the Chipped Pot.
The Chipped Pot will only work on authentic Sinisteas and the Cracked Pot will work on only counterfeit Sinisteas, so attempting to use either item is the easiest way to tell which form a Sinistea has. Using either item on the corresponding Sinistea form will produce a Polteageist. Both Polteageist's secret, authentic form and normal, counterfeit form immediately learn the signature move Tea Time when evolved, which forces all Pokemon in battle to consume any berries they're holding.
Pokemon Sword and Shield released on November 15, 2019 for the Nintendo Switch.