As a concept introduced within the Pokémon Global Link in Pokémon Black & White, X & Y continues the a new method of getting events, the serial code. Here, you get given a unique serial code within certain events or releases. When you enter the Serial Code, you're connected to the Internet to download the event. The serial code will then no longer work.

Quick Ball
Release Dates:

Japan: October 12th 2013
England: October 12th 2013

Gift:
12 Quick Balls

Method:
In Japan, you could receive the Serial Code for the 12 Quick Balls for purchasing the game at the Pokémon Centers across Japan
In the United Kingdom, you can receive the Serial Code for the Quick Balls by purchasing a marked copy of Pokémon X & Y from the Tesco supermarket.

CoroCoro Garchomp
Release Dates:

Japan: November 15th 2013 - August 29th 2014

Gift:
Garchomp

Method:
In Japan, within the CoroCoro issue released on November 15th 2013, there is a special unique Serial Code that, once entered, gives a download of a special Garchomp. This download will only be accessible until the end of August 2014

ガブリアス
Level 48
OT:コロコロ
ID:11153
Ability:Sand Veil
Hold Item:

Dragon Fang
Any Nature.
Date of Receiving
Pokémon Event. Apparently had a fateful encounter at Lv. 48
Draco Meteor
Dragon Claw
Dig
Crunch
Walmart Garchomp & Scizor
Release Dates:

North America: November 27th 2013 - June 30th 2014

Gift:
Garchomp (X), Scizor (Y)

Method:
In North America, various Wal-Mart stores are including a special serial code for Garchomp in new Pokémon X copies and Scizor in new Pokémon Y copies.

Garchomp
Level 50
OT:WINTER2013
ID:11153
Ability:Sand Veil
Hold Item:

Dragon Fang
Any Nature.
Date of Receiving
A lovely place. Apparently had a fateful encounter at Lv. 50
Slash
Dragon Claw
Dig
Crunch
Scizor
Level 50
OT:WINTER2013
ID:11153
Ability:Swarm or Technician
Hold Item:

Silver Powder
Any Nature.
Date of Receiving
A lovely place. Apparently had a fateful encounter at Lv. 50
X-scissor
Night Slash
Double Hit
Iron Head
Lucky Egg
Release Dates:

Japan: December 21st 2013 - December 26th

Gift:
1 Lucky Egg

Method:
In Japan, you could receive the Serial Code for the Lucky Egg at the Pokémon Centers across Japan, as well as Toys 'R' Us stores, if you brought a copy of Pokémon Black, White, Black 2 or White 2 to the event as well as Pokémon X or Y

CoroCoro/GAME Charizard
Release Dates:

Japan: March 15th 2014 - August 29th 2014
UK: July 11th 2014 - August 10th 204

Gift:
Charizard with Charizardite Y (X), Charizard with Charizardite X (Y)

Method:
In Japan, the magazine CoroCoro's April issue contains a special serial code which gives played a Charizard. The Charizard comes holding the Mega Stone for Charizard that is unavailable in the game, so Pokémon X players get Charizardite Y and Pokémon Y players get Charizardite X. This distribution also ran in the UK at GAME stores where you could either download in store, or get the Serial Code

Charizard
Level 36
OT:コロコロ
GAME 2014
ID:03154
07114
Ability:Blaze
Hold Item:

Charizardite X
Any Nature.
Date of Receiving
A lovely place. Apparently had a fateful encounter at Lv. 36
Dragon Rage
Fire Fang
Air Slash
Dragon Claw

Charizard
Level 36
OT:コロコロ
GAME 2014
ID:03154
07114
Ability:Blaze
Hold Item:

Charizardite Y
Any Nature.
Date of Receiving
A lovely place. Apparently had a fateful encounter at Lv. 36
Fire Fang
Flamethrower
Air Slash
Inferno
GAME Electabuzz & Magmar
Release Dates:

United Kingdom: April 4th 2014 - ??
France, Germany, Italy: April 14th 2014 - ??
Netherlands: April 14th 2014 - April 30th 2014
Spain, Portugal: April 14th 2014 - June 1st 2014
Australia: April 11th 2014 - May 11th 2014

Gift:
Magmar (X), Electabuzz (Y)

Method:
In Europe & Australia, to celebrate a new promotion to push Pokémon, various game specialist stores were offering free download codes for Magmar for Pokémon X players and Electabuzz for Pokémon Y players. These Pokémon come holding their evolution item.

Electabuzz
Level 30
OT:SPRING 2014
ID:04014
Ability:Vital Spirit
Hold Item:

Electirizer
Any Nature.
Date of Receiving
Lovely place. Apparently had a fateful encounter at Lv. 30
Low Kick
Shock Wave
Light Screen
Thunder Punch
Magmar
Level 30
OT:SPRING 2014
ID:04014
Ability:Vital Spirit
Hold Item:

Magmarizer
Any Nature.
Date of Receiving
Lovely place. Apparently had a fateful encounter at Lv. 30
Smokescreen
Fire Spin
Confuse Ray
Fire Punch

Movie Darkrai
Release Dates:

Japan: April 18th 2014 - September 30th 2014
United Kingdom: February 13th 2015 - May 5th 2015

Gift:
Darkrai

Method:
In Japan, when you prebook the ticket to the movie, Cocoon of Destruction & Diancie, you will be eligible for a download of the Pokémon, Darkrai. Unlike previous pre-booking distributions, this one is distributed via a serial code found on the ticket. It has the special move of Phantom Force..

ダークライ
Level 50
OT:ふしぎのくに
ID:04194
Ability:Bad Dreams
Hold Item:

Enigma Berry
Any Nature.
Date of Receiving
Pokémon Movie 14. Apparently had a fateful encounter at Lv. 50
Dark Void
Dark Pulse
Phantom Force
Dream Eater
Master Ball
Release Dates:

Japan: July 19th 2014 - September 30th 2014

Gift:
Master Ball

Method:
In Japan, when you have the special download only title, The Band of Thieves & 1000 Pokémon and take it to see the movie, Diancie & The Cocoon of Destruction, you will have the ability to download a mission for that game. If you complete the mission, you will get access to a Master Ball. The game will give you the serial code for it which can be retrieved in X & Y. You will receive one Master Ball .

PokéBall Pattern Vivillon
Release Dates:

Germany: August 14th to August 17th 2014

Gift:
Vivillon

Method:
In Cologne in Germany, in the Gamescom game convention, you have the ability to go to receive a special Serial Code. This Serial Code gets you the special PokéBall Pattern of the Pokémon Vivillon.

Heracronite & Pinsirite
Release Dates:

North America: August 18th to August 31st2014

Gift:
Heracronite (X)
Pinsirite (Y)

Method:
In North America, for a short time, you can go to Gamestop stores in the USA, or through the Pokémon Trainer Club newsletter in Canada & Latin America, and receive the special gift of a Heracronite if you're playing Pokémon X or a Pinsirite if you're playing Pokémon Y. This goes in tandem with the gift being distributed over the Nintendo Network at the same time, which gives a Heracross for X and a Pinsir for Y.


Shiny Mega Gengar Event
Release Dates:

North America: October 12th 2014 - October 26th 2014
Europe: October 15th 2014 - November 5th 2014

Gift:
Shiny Gengar

Method:
In North America, for a short time, you can go to Gamestop stores in the USA, or GAME in the UK and receive a special Shiny Gengar which holds the Mega Stone, Gengarite

Gengar
Level 25
OT:OCT2014
ID:10134
Ability:Levitate
Hold Item:

Gengarite
Any Nature.
Date of Receiving
Pokémon Event. Apparently had a fateful encounter at Lv. 25
Shadow Ball
Sludge Wave
Confuse Ray
Astonish
Diancie Event
Release Dates:

North America: October 27th 2014 - November 16th 2014
Europe: November 6th 2014 - November 28th 2014

Gift:
Diancie

Method:
In North America, for a short time, you can go to Gamestop stores in the USA, or GAME in the UK and receive a special Pokémon, Diancie, which cannot be obtained during normal gameplay

Diancie
Level 50
OT:OCT2014
ID:10274
Ability:Clear Body
Hold Item:

Normal Gem
Any Nature.
Date of Receiving
Pokémon Movie 14. Apparently had a fateful encounter at Lv. 50
Diamond Storm
Reflect
Return
Moonblast
Serena's Fennekin Event
Release Dates:

Japan: February 26th 2015 - March 31st 2015

Gift:
Fennekin

Method:
Following on from the change in Serena's appearance and the at the time upcoming evolution of Fennekin in the anime, a distribution of the Fennekin has been released on all games using a shared Serial Code revealed with the episode on February 26th 2015

フォッコ
Level 15
OT:セレナ
ID:02265
Ability:Blaze
Hold Item:

Destiny Knot
Any Nature.
Date of Receiving
A lovely place. Apparently had a fateful encounter at Lv. 15
Scratch
Flamethrower
Hidden Power
 
Movie Arceus Event
Release Dates:

Japan: March 7th 2015 - August 31st 2015

Gift:
Arceus

Method:
To tie in with the movie, The Archdjinni of the Rings - Hoopa, an Arceus is distributed to those who prebook the tickets. All players who pre-book tickets will get a serial code for use in Pokémon X, Y, Omega Ruby or Alpha Sapphire and this code downloads on of 18 different Arceus. The Arceus comes holding either the Silk Scarf or any of the 17 type plates at random, chosen when you download the Pokémon

アルセウス
Level 100
OT:デセルシティ
ID:03075
Ability:Multitype
Hold Item:

Silk Scarf
Any Nature.
Date of Receiving
Pokémon Movie 15. Apparently had a fateful encounter at Lv. 100
Judgment
Blast Burn
Hydro Cannon
Earth Power
7-11 Movie Events
Release Dates:

Japan: July 18th 2015 - July 31st 2015 & August 1st 2015 - August 16th 2015
August 17th 2015 - September 15th 2015

Gift:
Pikachu, Pancham, Lugia, Latios

Method:
To coincide with the release of the movie, Hoopa & The Clash of Ages, 7-11 stores in Japan gave access to special serial codes for Pikachu and Pancham, based on Ash's Pikachu and Serena's Pancham respectively in July, and Latios & Lugia in August. These were then later given at Pokémon Centers in Japan.

ピカチュウ
Level 50
OT:サトシ
ID:00711
Ability:Static
Hold Item:

Light Ball
Naughty Nature.
Date of Receiving
A lovely place. Apparently had a fateful encounter at Lv. 50
Thunderbolt
Quick Attack
Iron Tail
Electro Ball

ヤンチャム
Level 30
OT:セレナ
ID:00711
Ability:Mold Breaker
Hold Item:

Black Glasses
Adamant Nature.
Date of Receiving
A lovely place. Apparently had a fateful encounter at Lv. 30
Arm Thrust
Stone Edge
Dark Pulse
 

ラティオス
Level ?
OT:??
ID:00711
Ability:Levitate
Hold Item:
No Item
Any Nature.
Date of Receiving
A lovely place. Apparently had a fateful encounter at Lv. ?
 
 
 

ルギア
Level ?
OT:??
ID:00711
Ability:Pressure
Hold Item:
No Item
Any Nature.
Date of Receiving
A lovely place. Apparently had a fateful encounter at Lv. ?
 
 
 
Hoopa Distribution
Release Dates:

Singapore: August 21st 2015 - November 30th 2015
Europe: October 16th 2015 - November 5th 2015

Gift:
Hoopa

Method:
You can get Hoopa when you visit GAME stores in the UK from October 23rd to November 5th, Gamestop stores in Germany from October 16th 2015 to November 7th 2015. In addition to that, Maxsoft ran two Serial Code distributions for Taiwan and Singapore to receive Hoopa

Hoopa
Level 50
OT:Harry
Manesh
ID:10235
08195
Ability:Magician
Hold Item:

Focus Sash
Any Nature.
Date of Receiving
A lovely place. Apparently had a fateful encounter at Lv. 50
Hyperspace Hole
Nasty Plot
Psychic
Astonish
Pokémon XY & Z - Legendary Distributions
Release Dates:

Japan: October 29th 2015 - January 12th 2016

Gift:
Shiny Xerneas, Shiny Yveltal, Zygarde

Method:
To coincide with the release of the new series of the anime, Pokémon XY & Z, a promotion runs in order to provide the three legendary Pokémon of Kalos. However, the unique feature of two of these are that they are distributed as Shiny Pokémon, which has been impossible up to now. The Pokémon are obtained via Serial Codes which are distributed during the Pokémon XY & Z episodes set to air on October 29th, November 5th and November 12th respectively

ゼルネアス
Level 100
OT:XY&Z
ID:10295
Ability:Fairy Aura
Hold Item:
No Item
Any Nature.
Date of Receiving
??. Apparently had a fateful encounter at Lv. 100
Geomancy
Moonblast
Aromatherapy
Focus Blast

イベルタル
Level 100
OT:XY&Z
ID:11055
Ability:Dark Aura
Hold Item:
No Item
Any Nature.
Date of Receiving
??. Apparently had a fateful encounter at Lv. 100
Oblivion Wing
Sucker Punch
Dark Pulse
Foul Play

ジガルデ
Level 100
OT:XY&Z
ID:11125
Ability:Aura Break
Hold Item:
No Item
Any Nature.
Date of Receiving
??. Apparently had a fateful encounter at Lv. 100
Land's Wrath
Extreme Speed
Glare
Outrage


BREAKThrough Zoroark Event
Release Dates:

UK: November 6th 2015 - November 26th 2015

Gift:
Zoroark

Method:
In the United Kingdom, to celebrate the release of the BREAKThrough TCG set, a Zoroark was made available in GAME via Serial Code

Zoroark /
Level 50
OT:Sly
ID:11065
Ability:Illusion
Hold Item:
No Item
Any Nature.
Date of Receiving
A lovely place. Apparently had a fateful encounter at Lv. 50
Sludge Bomb
Dark Pulse
Flamethrower
Sucker Punch
20th Anniversary - Mew
Release Dates:

US: February 1st 2016 - February 24th 2016 (Expires May 31st)

Gift:
Mew

Method:
To celebrate the 20th anniversary, in February if you go to Gamestop during the time period, you can get a Serial Code to receive a Mew to your games

Mew
Level 100
OT:GF
ID:02016
Ability:Synchronize
Hold Item:
No Item
Any Nature.
Date of Receiving
a lovely place. Apparently had a fateful encounter at Lv. 100
Pound
 
 
 
20th Anniversary - Darkrai
Release Dates:

US: May 1st 2016 - May 24th 2016

Gift:
Darkrai

Method:
To celebrate the 20th anniversary, in May if you go to Gamestop during the time period, you can get a Serial Code to receive a Darkrai to your games

Darkrai
Level 100
OT:GF
ID:05016
Ability:Bad Dreams
Hold Item:

Enigma Berry
Any Nature.
Date of Receiving
a lovely place. Apparently had a fateful encounter at Lv. 100
Dark Void
Ominous Wind
Nightmare
Feint Attack
20th Anniversary - Arceus
Release Dates:

US: August 1st 2016 - August 24th 2016

Gift:
Arceus

Method:
To celebrate the 20th anniversary, in August if you go to Gamestop during the time period, you can get a Serial Code to receive a Arceus to your games

Arceus
Level 100
OT:GF
ID:08016
Ability:Multitype
Hold Item:
No Item
Any Nature.
Date of Receiving
a lovely place. Apparently had a fateful encounter at Lv. 100
Judgment
Recover
Hyper Beam
Perish Song
20th Anniversary - Genesect
Release Dates:

US: November 1st 2016 - November 24th 2016

Gift:
Genesect

Method:
To celebrate the 20th anniversary, in November if you go to Gamestop during the time period, you can get a Serial Code to receive a Genesect to your games

Genesect
Level 100
OT:GF
ID:11016
Ability:Download
Hold Item:
No Item
Any Nature.
Date of Receiving
a lovely place. Apparently had a fateful encounter at Lv. 100
Techno Blast
Magnet Bomb
Solar Beam
Signal Beam