What type of bug are you reporting? Teambuilder
What is the bug?
The Pokemon "Polteageist-Antique" specifically is missing the move "Celebrate" in the Showdown implementation in Gen8 and Gen9 natdex (tested in teambuilder formats "[Gen 8] Natdex Draft", "[Gen8] Draft", "Natdex Draft" and "[Gen 8] National Dex" (likely every format, where it should get it)), it should however learn the move.
There was an Event Sinistea-Antique that got "Celebrate" in Gen 8, this is correctly implemented in Showdown, this Sinistea-Antique can evolve into Polteageist-Antique" like any Sinistea could, so it can keep the move and use it as Polteageist-Antique
The Showdown-Implementation matches what is shown on Bulbapedia and PokemonDB, both of which have the same error (Sinistea-Antique having the move, Polteageist-Antique not having it), so it was likely an error in the data Showdown uses or they all use
On Serebii it is correctly shown that Polteageist-Antique learns the move through its pre-evo (https://www.serebii.net/pokedex-swsh/polteageist/ , segment "Pre-Evolution Only Moves")
Since the move has actual uses with Z-normal Celebrate this can actually make a difference, even if small (in formats Gen8+ with Polteageist-Antique and Z-Moves both being legal or just any draft format)
Are you able to replicate it? If so, how?
1. Go to one of the above mentioned formats in teambuilder (e.g. "NatDex Draft")
2. Give the move "Celebrate" to Polteageist-Antique
3. Validate
4. Get "Polteageist-Antique can't learn Celebrate." message (incorrect)
What is the bug?
The Pokemon "Polteageist-Antique" specifically is missing the move "Celebrate" in the Showdown implementation in Gen8 and Gen9 natdex (tested in teambuilder formats "[Gen 8] Natdex Draft", "[Gen8] Draft", "Natdex Draft" and "[Gen 8] National Dex" (likely every format, where it should get it)), it should however learn the move.
There was an Event Sinistea-Antique that got "Celebrate" in Gen 8, this is correctly implemented in Showdown, this Sinistea-Antique can evolve into Polteageist-Antique" like any Sinistea could, so it can keep the move and use it as Polteageist-Antique
The Showdown-Implementation matches what is shown on Bulbapedia and PokemonDB, both of which have the same error (Sinistea-Antique having the move, Polteageist-Antique not having it), so it was likely an error in the data Showdown uses or they all use
On Serebii it is correctly shown that Polteageist-Antique learns the move through its pre-evo (https://www.serebii.net/pokedex-swsh/polteageist/ , segment "Pre-Evolution Only Moves")
Since the move has actual uses with Z-normal Celebrate this can actually make a difference, even if small (in formats Gen8+ with Polteageist-Antique and Z-Moves both being legal or just any draft format)
Are you able to replicate it? If so, how?
1. Go to one of the above mentioned formats in teambuilder (e.g. "NatDex Draft")
2. Give the move "Celebrate" to Polteageist-Antique
3. Validate
4. Get "Polteageist-Antique can't learn Celebrate." message (incorrect)