On December 10th, 2021, the official Japanese Twitter account reminded people that this episode was available to watch on the official Japanese YouTube channel. The video was region locked to Japan only. It was available from December 10th, 2021 to December 17th, 2021. This episode was specifically labeled as a limited time broadcast (期間限定配信).

Pocket Monsters Anime Episode 90 'Dialga & Palkia! The Decisive Space-time Battle!!'
What did you think!?
Nyarth is upset because he can't speak human language due to the effect of time reversing.
Poor thing, but... he was so cute.
Anipoke Episode 90 will be available for one week from today!
Please check it out!

アニメ「ポケットモンスター」第90話「ディアルガ＆パルキア！時空大決戦！！」
いかがでしたか⁉
時間が戻った影響で人間の言葉を話せず慌てるニャース
可哀想だけど…可愛かったですね
アニポケ 第90話の公開期間は本日より1週間!!
ぜひご覧ください

The official Japanese Anime PR Twitter account posted a behind-the-scenes look at the making of this Anipoke episode with production info on December 9th, 2021.

Anipoke Production Secrets [Part 4]
Anipoke Winter Special Episode On Friday, December 10th, episode 90, "Dialga & Palkia! The Decisive Space-time Battle!!" will air. We asked Shuhei Yasuda, the character designer, about the highlights of the episode.
Satoshi, Go, Koharu, Hikari...what will happen to the Pokémon⁉
Please check it out!

アニポケ 制作秘話[その4]
アニポケ「冬のスペシャルエピソード」
12/10(金)は、第90話「ディアルガ＆パルキア！時空大決戦！！」を放送!
そこでキャラクターデザイン安田周平 さんに見どころをお聞きしました
サトシ、ゴウ、コハル、ヒカリ…ポケモンたちはどうなるの⁉
ぜひご覧下さい

Following Hikari in episode 89, Satoshi, Go, and Koharu appear in another world in episode 90.
The voice acting in each of their appearances, and when they revert to being little kids, is amazing!
The scenes with the little Satoshi, Go, Koharu, and Hikari are especially dear to me because they are so lovable and the pictures are so cute.
Character Design Shuhei Yasuda

第89話のヒカリに続いて、第90話では別世界のサトシ、 ゴウ、コハルが登場します。
それぞれの登場シーンと、小さな子に戻ってしまった時の 声優さんのお芝居が素晴らしいです！
その小さなサトシ、ゴウ、コハル、ヒカリのシーンは、健気で 絵も可愛いので特に思い入れがありますね。
キャラクターデザイン 安田周平

CoroCoro Comic's Official website posted an article about this episode just before the original airing on December 10th, 2021. They also tweeted about the page on the official CoroCoro Comic Twitter account to promote it.

It's almost time for Anipoke! I, too, am Satoshi from Masara Town! Who he met in a mysterious world... is another Satoshi!?


The anime "Pocket Monsters" will start airing soon! It airs every Friday at 6:55 p.m. and it is very popular! In this article, we'll introduce you to the Pokémon and characters that will appear in today's episode, as well as comments from the voice actors and director, and other Anipoke information you won't find anywhere else! The second half of the two-episode Anipoke Winter Special!


Satoshi and his friends arrive in another world that looks just like their usual world. But it's a world without Pokémon! Satoshi meets another Satoshi who looks just like him! Why aren't there any Pokémon here?

Satoshi said that one day, time for Pokémon began to go backwards, and the Pokémon that had evolved returned to their pre-evolution forms, forgot the moves they had learned, and eventually returned to their eggs.


▲ In the other world, Satoshi's Pikachu turned back into an egg, just like this.

And what do you know, the phenomenon starts happening to Satoshi's... (Oh, that's the usual Satoshi!) It starts to happen to Satoshi's Pikachu as well...!　

Satoshi and his friends (that's both of them) head to the Pokémon Center in Masago Town, where Professor Nanakamado is investigating the cause of this strange phenomenon!


▲ There's also something wrong with Satoshi's Pikachu and Go's Aceburn...!


▲ Satoshi's Pikachu turned into a Pichu!

Professor Nanakamado suspects that the legendary Pokémon Dialga and Palkia, which control time and space, are involved in this strange phenomenon.

To stop this phenomenon, Satoshi and his friends head for the Spear Pillar at the top of Mount Tengan!　Will they be able to save the Sinnoh Region?


▲ Dialga and Palkia clash violently! Is this the cause of the strange phenomenon!


▲ Go's Aceburn returns to a Hibanny!?


▲ The mysterious time phenomenon begins to happen not only to Pokémon, but to humans as well!


▲ If this battle can be stopped, will everything return to its original state...!?

So, the winter special is coming to its climax! Don't miss the epic ending, as it's just like a movie!

アニポケまであとちょっと！】オレ「も」マサラタウンのサトシ！ 不思議な世界で出会ったのは…もうひとりのサトシ!?
オレ「も」マサラタウンのサトシ！ 不思議な世界で出会ったのは…もうひとりのサトシ!?
毎週金曜よる6時55分から大好評放送中！
アニメ「ポケットモンスター」まもなく放送スタート！
この記事はアニメ放送直前に、今日の放送回に登場するポケモンやキャラクターの紹介、声優さんや監督からのコメントなどなど、ほかでは聞けないアニポケ情報をお届けするコーナーだ！　2話連続のアニポケ冬スペシャル後半戦！
いつもの世界とそっくりなもう１つの世界へとやって来たサトシたち。そこはポケモンたちがいない世界だった！　そこでサトシが出会ったのは、なんと自分にそっくりなもうひとりのサトシ！　なぜここにはポケモンたちがいないのか。サトシが…（あ、これはもう１つの世界のほうのサトシのことです。）
サトシが言うには、ある日ポケモンたちの時間が逆行し始め、進化していたポケモンたちは進化前の姿へと戻り、おぼえていたわざを忘れ、やがてタマゴに戻ってしまったのだという。
▲もう１つの世界ではサトシのピカチュウもこの通りタマゴに戻ってしまっていた。
そしてなんと、その現象がサトシの…（あ、これはいつものサトシのことね！）サトシのピカチュウにも起こり始めてしまう…!!　
サトシたち（これはサトシ二人とも）は、この不思議な現象の原因を調べているナナカマド博士がいるというマサゴタウンのポケモンセンターへと向かう！
▲サトシのピカチュウとゴウのエースバーンにも異変が…!!
▲サトシのピカチュウがピチューになっちゃった!!?
ナナカマド博士は、この不思議な現象には時空をつかさどる伝説のポケモン・ディアルガとパルキアがかかわっていると予想する。
サトシたちはこの現象を止めるため、テンガン山の山頂にある「やりのはしら」へと向かう！　シンオウ地方の危機を救えるのか!?
▲激しくぶつかりあうディアルガとパルキア！　これが不思議な現象の原因!?
▲ゴウのエースバーンは、ついにヒバニーに戻ってしまう!?
▲なんと、時間が戻る不思議な現象がポケモンだけでなく人間にまで起こり始めてしまう!!
▲この戦いを止められたらすべてが元に戻る…のか!?
ということで冬スペシャルはクライマックスへ！　劇場版なみの壮大なラストを見逃すな!!

The official Japanese Anime PR Twitter account posted an After Story comic on December 12th, 2021 by #もじゃクッキー @mojacookie.

Anipoke Episode 90 After Story
I have a feeling that Satoshi, Go, Koharu, and Hikari from the other world are thinking the same thing...

I wonder if the other me is doing okay now?

アニポケ 第90話アフターストーリー
もうひとつの世界のサトシ、ゴウ、コハル、ヒカリも
きっと同じことを考えている…ような気がします

もうー人の 自分、 いまごろ 元気にしてる かな—?

The official Japanese Anime PR Twitter account posted a behind-the-scenes look at the making of this Anipoke episode with production info on December 11th, 2021.

Anipoke Production Secrets [Part 5]
What did you think of the "Winter Special Episodes" broadcasted on Friday, December 3 and Friday, December 10?
Another Satoshi, Go, and Koharu, who live in another world, also appeared.
It was interesting to see the differences in what each of them said and how they acted.
We asked General Director Hiroki Tomiyasu about the character themes he personalized.

アニポケ 制作秘話[その5]
12/3(金)、12/10(金)放送の「冬のスペシャルエピソード」いかがでしたか
別の世界に住む、もう1人のサトシ、ゴウ、コハルも登場し、
それぞれの発言や行動の違いも興味深かったですね
どのようなテーマで性格付けしたのか冨安大貴 総監督にお聞きしました

The characters from the other worlds have had their original personalities changed, each with a different theme.
The other Satoshi, is more timid, while Go is more confident. Koharu is the brainy one.
General Director Hiroki Tomiyasu

別の世界の登場人物は、それぞれ異なったテーマで元の 性格からずらしました。
もう1人のサトシは気弱な印象、ゴウはさらに自信家に。 コハルは頭脳#派といった感じです。
総監督 冨安大貴

The official Japanese Anime PR Twitter account posted a behind-the-scenes look at the making of this Anipoke episode with a production artwork piece on December 9th, 2021. The picture featured Satoshi's Pichu.

A glimpse behind the scenes of the Anipoke production
This time, from episode 90, it's a Pichu original drawing.
Satoshi's Pikachu becomes Pichu...
It's a scene of surprise.

アニポケ制作の舞台裏をチラ見せ
今回は第90話の中から
ピチュー の原画をご紹介
サトシのピカチュウ がピチューに…
突然の出来事にびっくり！のシーンです