These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
The most famous party is the Strange Klug ACI; from what we see in Fever 2, Klug does not like having his body rented out. However, fans will either say that the two are friendly rivals(mostly harming one another in comedic ways), the two hate each other, or the two don't mind one another. There's also small camp that turns Strange Klug into a demon that forces Klug to act evil, or is a psychopath.
Ekoro's ACI is simple. Was he a monster, a creature that loved Ringo, or a Yandere that loved Ringo?
Character Tiers: Maybe. They come from drop sets and chaining power in the fever/henshin modes. However, the matches seem to be skill > tier.
For drop sets, Arle is at least slightly better than everyone else due to her light, precise drop set (pairs only) so the pros can efficiently create their massive chains in whatever way they want to build it. Other drop sets are slightly to somewhat slower due to the higher odds of having an occasional puyo out of place and needing to work around it and generally more restricted to freestyling than patterns.
Bigger drop sets, however, can bring balance due to having more puyo on the field quickly and thus having material to harass the opponent with small chains or having an easier time getting into fever/henshin. Carbuncle, who has the "biggest" drop set in the game, is sometimes considered a Tier-Induced Scrappy because of this.
There are also chaining power tiers inside and outside fever/henshin, though those effects are subtle.
Complacent Gaming Syndrome Some people never play anything other than Tsu, and/or fever, and/or henshin modes (possibly playing only Arle or Carbuncle due to their drop set in fever/henshin). Good luck trying to find someone to play other modes like excavation.
Lemres: I appreciate the offer... But I apologize, I just don't swing that way.
And then there's Lemres to Oshare in this exchange.
Oshare: I would be madly in love with you. That is, if hadn't already met someone else before.
Lemres: Guess someone beat me to you long ago. What a shame. I wanted to meet you while you still had long blonde hair.
Launcher of a Thousand Ships: Schezo is currently paired with Arle, Rulue, Witch, Satan, Seriri, Lagnus, Incubus, Lemres, and Doppelganger Schezo. This is clearly not what he meant by "I want you!" at all.
Because Puyo Pop Fever taunts can be activated with the DS' microphone, playing the game in a moving vehicle with the sound on is NOT advised. "Youyouyouyouyouyou BETCHA!"
The English dub voices for Puyo Pop Fever... actually, the Japanese voices in that game were pretty bad too.
Narm: The voice acting in the English arcade game. On one hand, the woman that voices Arle speaks with virtually no enthusiasm. On the other hand, many of the other characters' intro quotes are easily more hammy than their Japanese counterparts. Skeleton-T's simple "Ocha!" becomes a low "Ohhhhh...cha!", Nasu Grave's "Otankonasu!"note "Fool!" is changed to "Mooooron!", Draco's cute little "Gau!" becomes a thunderous "Gaaaooooooaoaoh!", and it's hard not to grin when Schezo screams "Ariaaaa-duh!" with a horrible fake accent.
Sequel Displacement: When people talk about the "first" Puyo Puyo game, they are almost always referring to the arcade game instead of its MSX/FDS predecessor.
They Just Didn't Care: A small example from the first Puyo Puyo. In the arcade game and many of its home ports, each opponent greets the player with a vocal catchphrase before the battle begins. These voice clips are recycled from Madou Monogatari 1-2-3, which doesn't seem like an issue until one realizes that Rulue is only fought in the Game Gear version of III (released long after the original Puyo Puyo) and thus does not have a voice clip. Instead of recording a catchphrase for her, Compile simply plugged in one of the game's sound effects and called it a day.
The English version, on the other hand, has a few more examples: not only did they retain Rulue's silent treatment (despite recording new voices for the other characters), the "Puyo Puyo!!" voice clip from the title screen is used in place of the "Bayoen" spell, the voice clip that plays when "Silvana" loses is recycled from the clips that play when the opponent is building a chain, and they try to pass off Harpy as a "Dark Elf" by removing her wings and changing the color of her clothes. And that's before getting into some of the more ridiculous Dub Name Changes...
Uncanny Valley: Madou Monogatari: The Final Test's artstyle is unsettlingly different from the other Windows installments.
Oshare Bones. While not as often as other characters, his effeminate mannerisms, attraction to male characters, and usage of feminine Japanese speech have led some fans to initially believe he is female, despite Fever 2 officially listing him as male. This confusion seems to happen more often amongst Japanese fans.