This opening completely altered my brain chemistry as a kid and I've never been the same since.
it's so BOUNCY and FUN, even without words you can tell what moves each Pokemon is uses (Girafargig going for a Stomp, Butterfree using Sleep Powder/Gust) as well as visually showing how Quagsire is immune to electricity so Pikachu has to improvise, the personality/attitudes of each Pokemon really shines (Cyndaquil kinda just yawning like "OK, I'm awake, let's go" before immediately being able to shove off the Mankey, and then letting loose a big Flamethrower like it's nothing, just so casual), this is just a Battle for fun they aren't trying to knock out each other's entire teams so Ash and Lisa are happy to just have a tie at the end, the Pokemon use the environment of the playground as they Battle, both Trainers cheer and cuddle with their Pokemon through it all... it really is BEAUTIFUL
Just to add on to this sentiment, Lisa's not exactly a major character in the film right? This battle happens with her just kinda crossing paths with Ash and co, and then she leads them to the town where all the eventful stuff is actually happening. And yet despite that, they take the time here to clearly show her own attitude and that she has her own relationships with her pokemon. The specific ways she gets excited when they're doing well and disappointed when they lose their part of the fight, it really gives the impression that she's someone with just as full and eventful a journey as Ash has had.
