Hugtto PreCure had four crossover episodes, not counting the traditional last-episode handover cameo for the Pink Leader of the next series:
Eps.21-22 = guest-starring Honoka and Nagisa from Futari wa PreCure (2004-05).
Eps.36-37 = guest-starring every PreCure to date.
These crossovers are my favourite thing in Hugtto. It's a strong year with a lot to enjoy and admire, but these I love to pieces. I could watch them again and again. PreCure has lots of crossover movies, but this was the first time past PreCures returned in the TV show. (Unless you count the 10th anniversary cameo introductions in HappinessCharge.)
Also, more importantly, these episodes share my reverence for the original team of Honoka and Nagisa. (Yes, I realise there's also Shiny Luminous.) Ep.21 only drops them in at the cliffhanger, but I had to mention it anyway, because HOLY SHIT. Now that's what I call an introduction.
Ep.36 attempts something similar, but it falls flat in comparison. They're still cool, though. Sixteen PreCures have fought Dr Traum, but now the originals have arrived. Game over. The show hasn't forgotten that Nagisa and Honoka are officially the strongest. They never really used their magic much. They just kept punching the living shit out of monsters. Precure All Stars New Stage! Friend From The Future! (at the 57min point) gave them the famous boat scene, where the eleven Smile and Suite PreCures can barely hold back an ocean liner. It's got away from them and is building up speed when the Futari wa PreCures appear and simply stand in front of it. Wham.
Ep.22 only gives them one fight scene, but the animators pull out the stops for it. Then, in ep.37, Dr Traum has sixteen PreCures on the run when the Futari wa trio appear and flatten him. (There will be an even bigger fight later, mind you, with everyone. Incidentally, the sixteen were five from Hugtto, six from KiraKira, three from Mahoutsukai, Love from Fresh and Nozomi from Yes! PreCure 5. Mind you, that's arguably more like ten since the KiraKira girls barely count.)
That later mega-fight is pure joy, because its incidental music is DANZEN, the franchise's award-winning and awesome original theme song. PreCure has had some barnstorming songs over the years, but DANZEN remains definitive. There are franchises where you can just say The Music and it's obvious what you mean. Cutey Honey. Gegege no Kitarou. James Bond. Doctor Who. And, for PreCure fans who've been here since the beginning, it's DANZEN. (Mind you, I'd personally also put HeartCatch's music on that level.)
(My only regret is that none of these episodes use the DANZEN end credits from the Hugtto! Pretty Cure Futari wa Pretty Cure: All Stars Memories movie. They stick with the regular end sequences... and Hugtto's theme songs are nothing special.)
Discussing individual episodes:
EPISODE 21: "Big Rampage? The Pretty Cure Emiru Wants To Become!"
They only show up right at the end. But wow.
EPISODE 22: "Our Song Of Love! Let It Reach! Twin Love Guitar!"
The pre-credits catchphrase battle is a bit too cartoonish. "Arienai!" "Mechokku!" The episode as a whole though is a meaningful, important stage in the ongoing Hugtto story. The superhero battles aren't actually what's important, cool though they are. Nagisa and Honoka matter because they can say definitively (with flashbacks) that it's okay for friends to fight, which had been a barrier stopping Emile and Ruuruu from talking properly to each other. Finally, those two achieve that.
Then, on the villains' side, there's a love betrayal, despair and a pseudo-suicide.
EPISODE 36: "Hooray Hooray! The Big Gathering of the Legendary Pretty Cure!!"
To enjoy the first ten minutes, it helps not to have watched KiraKira PreCure a la Mode. That was me on first viewing. Happy days. They broke the franchise in 2017, frankly. Starting the episode with KiraKira was a downer, even with the Mahoutsukai girls appearing too.
Then, though, came the nostalgia rush of older characters and I loved PreCure again. Nozomi from Yes! PreCure 5 is almost a mandatory choice, but Cure Love from Fresh? That's a left field choice. And Bunbee!
EPISODE 37: "To The Future! Pretty Cure All For You!"
The KiraKira PreCures are used better this week, for what it's worth. Ep.36 cheated and had them punching and kicking (which they almost never used to do), but at least here they're doing their usual food attacks. Whipped cream, etc.
There's humour. There's a planet-level threat. Hana does her cheerleader "hooray" in the face of an army of darkness, which is the most important thing for Hugtto. (They fight, but it's not just fighting that wins the day.) There's a father-daughter connection for two unexpected characters, which the show would soon return to in ep.40. And, of course, there's everyone. 60 PreCures. Apparently you can spot relatively obscure ones like Cure Flower (Granny in HeartCatch), the hitherto movie-only Cure Echo and even Kaoru and Michiru (Splash Star).
I loved it to bits.