It's the twenty-minute mini-movie that was shown with the first Pokemon movie,
Mewtwo Strikes Back. It's also kiddie-oriented even by Pokemon standards, but in a fun and interesting way that I wish they'd pushed even further. I liked it.
The story involves Pikachu and his fellow monsters being unleashed upon a Pokemon-only holiday resort. Satoshi and the other humans appear right at the beginning ("have fun"), then right at the end ("did you have fun?"). That's it. No other humans appear. Everything in between is all about candy-coloured balls of monsterdom, who mostly can't speak except to repeat their own names over and over again with different intonation. That talking cat from Team Rocket shows up, but only to turn into Wile E. Coyote and make me laugh.
This could have been awesome! Imagine a Looney Tunes cartoon, but with Pokemon. No dialogue. No story beats that can't be communicated through action and facial expressions. Sounds great, doesn't it? You'd have all the usual action, visual gags and comedy, but with Pokemon superpowers. In fairness, the episode quite often goes there, with sequences like the runaway tree trunk and the one where Pikachu and a Raichu are so busy fighting each other that they don't notice that they keep trashing bigger, more badass Pokemon just by running past them.
However it's not like that all the time. Firstly, unlike Tom and Jerry, it's not primarily comedy. It's a story about not fighting and overcoming your differences to help people who need you, which is... um, not the focus of Tom and Jerry. The wacky visual comedy stuff is thus just one element in the episode.
Secondly (and more disappointingly), they cheat. There's a narrator. I don't mind Meowth/Nyaasu meowing out some of his tortured human-speak, because he's in the story and a comedy character to boot. However I do object when Pikachu runs between two groups of Pokemon to try to stop them fighting... and the narrator then explains to us that that's what we're looking at. This is bad for three reasons. Firstly, it's unnecessary. I can see what's happening for myself. I'm not blind. Secondly, it encourages laziness. If you need a narrator to help your audience understand blindingly obvious story beats like that, then your animators aren't doing their jobs properly... although that said, I think I'd have understood this particular episode fine with the sound turned down. Finally the third reason why I don't like the human narrator is simply the fact that I think it dilutes the good and fun idea of a Pokemon-only "no humans allowed" adventure.
The story isn't complicated, obviously. For what it is, it's still good, though. I like the Pokemons' characterisation. They're childlike and childish, keen to be obnoxious, start fights and sneer at each other. However at the same time, they're capable of being reasoned with and of working together in a important cause. This interplay is fun and I'd say they're more interesting like this than when they're with their human owners. Well, except for Pikachu-Satoshi, obviously.
Apparently the episode introduced two Pokemon that hadn't been seen before in anime: Snubbull and Marill. That probably won't mean much if you're not already a Pokemon fan, though. For me the most memorable Pokemon was the weird-looking Togepi, who's best described a starfish trapped in an egg. It also seems mentally undeveloped even compared to other Pokemon. It's a toddler and a crybaby. I liked it.
There's not a huge amount to talk about here, really. In length, it's a TV episode. It's a simple, fun story of monsters being childish at each other and regularly causing trouble. It's amusing, although not primarily a comedy. It's never annoying and Pikachu is still way more charming and likeable than I'd expected. Pokemon is good.