Symbiosis Eject Button glitch

The Symbiosis Eject Button glitch is present in the core series Generation VI games: Pokémon X, Y, Omega Ruby, and Alpha Sapphire.

The glitch was first documented by YouTube user 1212 Weedle in this video.

In Generation VII, the Eject Button no longer triggers, so the glitch does not occur.

Performing the glitch
If an ally's Eject Button is consumed, will activate and transfer an item to that ally after it switches out but before its replacement is sent out. Any item transferred in response to an Eject Button activating cannot activate at this time.

Effects
When this Pokémon is switched in again, the Pokémon's item will be affected by a glitch which may cause the item's effect to be applied twice. This behavior lasts until the Pokémon is switched out, or until the Pokémon's item is removed or moved to another Pokémon. The items affected by this glitch are:
 * Black Sludge will hurt or heal the holder twice per turn (the item activation animation will display each time).
 * Sticky Barb will hurt the holder twice (the item activation animation will display each time).
 * Life Orb will apply its damage boost twice, and decrease the holder's HP twice.
 * Rocky Helmet will inflict damage twice.
 * Destiny Knot will activate twice. If the other Pokémon has a Mental Herb, it will be used up upon the first activation, only to be infatuated again a second time.
 * Shell Bell will heal the holder twice (the item activation animation will display each time).
 * Leftovers will heal the holder four times (the item activation animation will display twice, once before applying, once after healing twice).
 * The applies twice. The two multipliers are applied in sequence, each capping after 5 uses of the move. This means that the move's power becomes 1.44× after 1 use (1.2×1.2), 1.96× after 2 uses, 2.56× after 3 uses, 3.24× after 4 uses, and 4× after 5 or more uses.
 * Stat-stage boosting held items, such as the Weakness Policy and Salac Berry, will boost stats twice (the item activation animation will only display once). The Starf Berry can increase a different stat each time.
 * and Berry Juice will heal twice (even if the Pokémon heals above the activation threshold after the first heal), unless they are activated upon switching in (in which case they will only activate once).
 * will quarter the damage instead of halving it (although the activation message will only be displayed once).
 * The Scope Lens and Razor Claw will boost the holder's critical hit stage by 2 instead of 1.
 * The following items have their passive boosts applied twice: Choice Band, Choice Specs, Choice Scarf, type-enhancing items (including Plates and Incense), stat-enhancing items (including the Assault Vest and Eviolite), Float Stone, Big Root, Iron Ball.

Some items are only affected in trivial ways:
 * The Quick Claw and Power Herb will display their activation messages twice.
 * The Air Balloon will display the floating message twice (but will only display the burst message once).

Unaffected
Gems and the Lansat Berry are unaffected. The moves, , , and are unaffected.