As a Hoenn enthusiast, I obviously loved its prominence in the opening here. Also, they showed Thunder Armor :0. Ambipom's presence was an odd choice though, since Ash never evolved it that far under ownership of any kind. I get it's a former Pokemon of Ash's that ended up evolving later (at that point it's wholly Dawn's Pokemon), but Aipom would have been more appropriate.
Always love seeing Ash rotate in his strongest Pokemon, even when it does nothing super significant. It's really a tremendous shame it hasn't done anything as notable as his later caught mons since dominating pre-champion Iris's Dragonite (unless it came back and did something in some JN that I haven't seen yet). Could have easily did what Alan's (and Leon's) Charizard did, if not more.
Pikachu wearing that Squirtle Squad merch, gotta love it.
They almost had me fooled for a second during that Team Rocket reveal on stage, when I thought they did a return to their black attire from BW. Those power ranger-like outfits on the squirtle squad, when did... okay. The high popularity of the squad is well deserved with how long they been putting out fires there.
The combination of Brock getting the Poison Jab from Croagunk and Ear-pull from Misty was entertaining. Like how he actually had Croagunk with him. Tells us it hasn't evolved, but I don't see the problem with an evolution at this point in the series.
So... the nostalgia factor overall wasn't too effective with how much reunions there's been since S&M. It worked better when there were whole series long gaps pre-S&M before seeing them again. Throwing in like Pidgeot would have up-ed the effectiveness of the nostalgia, though they also could have used more memorable flashbacks as well. Squirtle gave Ash a hug far later in the episode that actually felt very reminiscent of something in the OS. And I know some people never get tired of the gang of 4, but it'd be cool to add another familiar-with mon after all their reunions prior. (I like how I immediately knew a thunderbolt was coming once the other starters used their moves on Ash. "Flamethrower'ed, Razor Leaf'ed, and Water Gun'ed? Ok Pika's Thunderbolt is coming next lol".)
The episode was decent, but it's last several minutes that had the strongest impact and made it very enjoyable. Once Brock lent his assistance during the final fire scene, everything from then on was near-perfect. Everybody did something, played a part. Misty brought out her water mons, including Clauncher (good move). Ash raises Squirtle's spirit after seeing it in a pinch, leading to it (and the squad) then having a flip-hat-backwards-like moment by changing to the original attire (thankfully lol). Ash got some water hoes, which Misty then connected. Despite the poor animation, Pikachu then negated something in Ash's way with thunderbolt. The scene escalates, pushing Charizard and Bulbasaur to step up and participate. Wild Pokemon (which happen to be the same bunch seen throughout the episode) are spotted on the rooftop, extending participation and a higher level of teamwork for the starter trio. Ash himself even directed most of the dramatic event, with the Hall of Fame BGM fittingly played over. The cons I'd give that whole particular setpiece are the weak animations in areas, the still-shots, Squirtle using Water Gun over Hydro Pump (like, why? You have Hydro Pump and Misty's Politoad used it on the fire so...), and Brock doing literally nothing else after claiming to "evacuate" as the subs say (when all we're shown is Brock blocking a wide line of people from the center in one spot, and later shown staring at the fire with people still close by lol. I expected for his Pokemon to come out and use ground attacks and such against the fire, as been seen before, but it didn't happen).
Naturally everyone made up. Personally, always been proud of Squirtle and what it's achieved, but it's always been like off-putting seeing Ash's other starters under his ownership and ready for transfer while he's out there with an actual occupation. Being... Together Forever... would be sweet. Lastly, one of my favorite parts, Ash being recognized as the champion he is, with a whole crowd of people rushing over to him. But not even just Ash, Misty and Brock received the same attention for their gym leader roles. Everyone was popular (except Bulbasaur and sadly Charizard. Speaking of which, I kinda wish one of the kids asked: "Woah, you also have a Charizard like Leon? Who's is stronger?!" hahaha).
There's always more to say, always, but time is limited. I do have a wish I hope happens though. I know the English dub is more explicit about about the promise to return to Pidgeot than the JPN dub, but I really hope it and Ash reunites, and is ridden, before the closure of Ash's journey.