Without a doubt, this was One of the best episodes of the BW series.
It's annoying when Iris called Ash a kid for getting excited for the Kanto Festival, but I liked how Cilan told her that she's a kid herself. The Kanto Festival itself was interesting, there even was the Magikarp salesman. It's great to see Prof. Oak and Tracey getting appearance, too bad Tracy didn't get a speaking role but I'm glad he appeared.
Charmander's trainer was cute and the Charmander itself was cool, too bad Charmander hurt itself during showing of it's 'signature move' Ember to the others.
It's great to see Ash explaing the history of Charizard.....one of his strongest Pokémon. The flashbacks from the previous sagas were incredible, all of the scenes from the older episodes looked fantastic in BW style. It's awesome that we got to see all of Charizard's best moments, as well as Ash in his OS and AG outfit. The re-animated scenes were so much better than the outdated original scenes. We got to Primape and Pidgeotto too...... *Sigh* it's a shame that we didn't got a reunion episode with them, but I'm glad they appeared in the anime after so long(even though they only appeared in flashbacks).
Then there were flashback appearances from Damien, Liza and Koga. They all looked cool in their new appearances. It's cool to see the Squirtle, Charmender, Bulbasaur and Pidgeotto in the heartwarming scene from "Snow Way Out!", that scene is one of the best scenes from the Kanto Saga in my opinion. TPCI even kept the same dialougs from the original episodes.
It was surprising when Prof. Oak said that Charizard retured from Charicific Vally to his lab and it's even more surprsing when Ash sent Unfezant to Prof. Oak for BRINGING CHARIZARD IN UNOVA!! It's cool to see Ash sending out Charizard, his roar was epic! It's awesome to see Ash and Charizard finally reuniting after so long.
That fist bump was cool.
I loved how Charizard completely dominated Iris's Dragonite in the battle, it made Ash look like a strong trainer. I really wanted Charizard to defeat Dragonite, but........N stopped the battle! Ugh....why did you do that N? The battle was getting really good and you had to ruin it...meh.
It's hilarious when Iris thought Charizard was Dragon Type! I LOL'd at her facial expression when Ash dexed Charizard and showed it to her. Iris always calls Ash a 'kid' for the simplest things, but in this episode, she's the one who's a 'kid'. Serves her right.
I'm so glad that Charizard is staying with Ash instead of going back to Charicific Vally, it's one of the best things the writers have done to the anime.
I was never the biggest fan of the 4kids voice cast, so the TPCI voices didn't bother me in the flashbacks. All of the characters (except Misty)sounded fine to me.
My only complaint about this episode is Charizard's moveset. Why did the writers replaced Seismic Toss with Slash? Seismic Toss was Charizard's signature move, so it's kinda disappointing to see Charizard not being able to use the move anymore. Other than that, it's an amazing episode.
I would have liked it if Tracey had gotten to say something too, but then again if he would have sounded like he did in "Home is Where the Start Is" it wouldn't have been worth it. I did like Cilan comparing the stories of Charizard with Iris's experiences with Excadril and Dragonite. Iris's reaction to learning Charizard isn't part dragon type was funny too. 
