There's one question that often lingers in the back of a Pokémon fan's mind, ever since the series started over 25 years ago: What's it like inside a Poké Ball? Pokémon Horizons has offered one answer to that question, and as it turns out, it's not half bad.
Pokémon spend a lot of time inside their Poké Balls, and fan conceptions of what it's like for these Pokémon have varied greatly. Many assume that Pokémon are just in some sort of stasis, converted to energy or data, and are unaware of the passage of time while inside the ball. Some think it's fairly nice in there, with everything a creature could need. Others assume that being in a Poké Ball must be rather unpleasant--why else would Ash's Pikachu be so averse to it? In very early artwork, Pokémon are shown as literally just shrinking down and fitting inside the ball, suggesting that the inside of the ball is just that: the empty internal space that's seen when it opens. Now, the newly rebooted Pokémon Horizons has tossed its concept of the Poké Ball interior out there through a segment in the fifth episode.
In the episode, the streamer known as Nidothing releases a video on Poké Balls, which Roy watches within the show. Nidothing and their Quaxly demonstrate a few different types of Poké Balls, but when it gets to the Luxury Ball, it actually provides a view of the interior. Inside is Quaxly relaxing on a couch, sipping on a beverage in a stemmed glass with a disco ball overhead and what appears to be a full bar in the background. The moment was picked up on by Joe Merrick, the founder of the notable Pokémon fansite Serebii.
Luxury Balls are the most expensive variety of (mass-produced) Poké Ball in the games; they have a catch rate on par with a regular Poké Ball, but Pokémon captured by these balls automatically become more friendly, which is implied to be due to the nicer conditions. While the segment in the episode is merely Nidothing's visualization of that concept, it's the closest the series has ever come to actually giving an idea of what the interior of a Poké Ball is like. Many Poké Ball fan works in the past have done similar concepts--even Adult Swim's Robot Chicken once had a bit where Pikachu partied inside its Poké Ball, complete with a disco ball hanging from the ceiling like Quaxly's.
While the Pokémon anime has finally provided some sort of answer as to what a Poké Ball is like, the debate will certainly rage on. Due to the video-within-a-video nature of the scene, it's probably not meant to be taken too seriously, but fans are free to imagine their own Pokémon relaxing like this in their Poké Balls.
Source: @JoeMerrick/Twitter