Summary of "Pokémon Sword and Shield's "Rare Shinies" (that are actually common)"

Core idea

Sword & Shield (and some other Pokémon games) display two visual shiny variants: star sparkles and square sparkles. Square sparkles are generally treated as the rarer/desirable variant, but the actual star vs square split depends entirely on how the game generates that specific Pokémon (its origin and whether a “force shiny” routine ran).

Shininess is determined from a Pokémon’s Personality Value (P).
Different generation mechanics and encounter methods produce different distributions of P, so star/square odds are not a single fixed probability — they vary widely by method and game.

Short takeaway: whether a shiny is a star or a square depends on how the game produced that Pokémon, not on a universal visual probability.

How the “force shiny” function breaks the intended distribution

Since Generation VI, many methods use a “force shiny” routine: the game ensures an encounter is shiny by overriding or adjusting the generated Personality Value rather than relying solely on the random P roll.
When the force-shiny routine runs, results are heavily biased toward square sparkles. Many guaranteed/forced-shiny encounters end up square almost every time; the chance to be a star in those cases can be extremely small (the video cites an example on the order of ~1 in 4,369).
By contrast, methods that make many independent P-rolls (no force override) preserve the intended star:square ratio from that generation’s P-to-shiny rules, so star shinies remain common under those methods.

Encounter methods that call force-shiny (mostly produce square shinies)

These methods usually force the Pokémon to be shiny, and therefore tend to produce square sparkles:

Shiny patches from X & Y Poké Radar
DexNav shinies
Forced shinies from Ultra Sun / Ultra Moon wormholes (non-Legendary/UB)
All overworld Pokémon in Let’s Go Pikachu/Eevee
Overworld spawns or fishing in Sword & Shield
Poké Radar shiny patches in Brilliant Diamond & Shining Pearl
Scripted guaranteed shinies (examples: Ponyta in Legends: Arceus scripted encounter; some DLC scripted shinies in Scarlet & Violet; guaranteed raid-event Rayquaza)
Shiny transfers from Gen 1/2 Virtual Console via Pokémon Transporter
Scarlet & Violet union circle “outbreak” encounters (the encounter is a shared prop and the force-shiny function creates a shiny matched to the caught Pokémon for each trainer)
Legends: Arceus scripted shiny encounters and some hyperspace distortion spawns when sparkling power is applied

Methods that preserve the star/square ratio (do not rely on force-shiny)

These rely on extra independent P-rolls rather than forcing shininess, so they keep the generation’s usual star vs square odds:

The Masa method (and its iterations)
Shiny Charm (in games other than Let’s Go and Sword & Shield)
Chain fishing (Generation VI)
Friend Safari in X & Y
Non-scripted Legends: Arceus methods (research encounters, normal outbreaks)
Sparkling power and non-event outbreaks in Scarlet & Violet

Important exceptions and special rules

Fateful encounter flag (often used for event-distributed Pokémon): always appears as a square shiny regardless of Personality Value.
Pokémon originating from Pokémon GO: always appear as square shinies when transferred.
Pokémon that originate from the Max Raid layer (Max Raid in Sword & Shield): always appear as star shinies.
Scarlet & Violet union circle:
- Multiplayer changes the per-player forcing and thus the distribution.
- Single-player union circle behaves differently from multiplayer.
Event outbreaks with boosted odds may include both forced and non-forced sources in the same outbreak; star/square rates can therefore vary within the same outbreak.

Practical tips for shiny hunters

If you want a star shiny, avoid encounter methods that use force-shiny where possible (many overworld and guaranteed shinies). Prefer methods that rely on raw P-rolls (Masa method, shiny-charm chaining, Friend Safari–style repeated independent rolls).
If a shiny is from a guaranteed/event/fateful encounter or transferred from GO, expect a square shiny only.
For exact odds in a specific game/method, consult detailed charts or math resources — the underlying math differs by generation and method and can be fiddly.