Clear Sky. Is he a sympathetic antagonist with a believable Freudian Excuse, or is he just a hypocritical jerk who deserves to die?
Storm is either seen as an interesting and fun she-cat or a boring excuse to create romance drama.
Wind Runner became one due to her actions in Thunder Rising and The First Battle, in which she is shown to be a warmonger and fuels the rivalry between the Moor and Forest groups. Some people think that she's sympathetic and well written, while others hate her for these actions and want her to go down.
Jagged Peak, mainly due to his treatment of a newly returned Thunder in The First Battle. Was this behaviour understandable due to his experiences with Clear Sky? Or is he just a jerk?
Star Flower in A Forest Divided. Is she a Nice Girl who genuinely wants to be with Clear Sky and wants to be friends with Thunder again? Or is she a smug Manipulative Bitch who's faking being captured and trying to turn Clear Sky and Thunder against each other?
Slash. Is he a cool and genuinely menacing villain, or is he a boring ripoff of One Eye and a letdown compared to the other villains of the arc?
The time period of the series. Some fans like the idea of a prequel and think The Last Hope wrapped things up well, while other fans want to know what happens after the battle. However, it appears to be dying down with the positive reception of The Sun Trail.
The treatment of she-cats in The Sun Trail. Some fans think that the she-cats got shafted in terms of character development and the book is full of misogyny. Other fans don't agree and think the complainers are just being obsessive.
Thunder Rising is the most divisive book in the series, so far. Is it good, but not as good as The Sun Trail? Is it an Even Better Sequel? Is it a terrible waste of all of The Sun Trail's potential? It depends on who you ask.
Come for the deaths, stay for the character development.
Come for Gray Wing, stay for Tall Shadow (or Jagged Peak).
Continuity Lockout: After the amount generated by Power of Three and Omen of the Stars, this arc for the most part avoids it. Someone with no knowledge of the rest of the Warrior Cats series could pick up a copy of The Sun Trail and completely understand it. However, it still exists in small qualities. If this is a reader's first Warriors book, the beginning scenes featuring the Tribe will lose some of their impact, and the last chapter's rather awe-inspiring reveal about Thunder will fall so flat that new readers won't even realize that it's a twist.
Before the release of The Sun Trail, Silver Frost, a Tribe elder, got the most love out of the characters.
Now that The Sun Trail is out, the most popular characters are Tall Shadow and Jagged Peak, the former of which has already spawned her own meme.
River Ripple has been declared by many to be the best part of Thunder Rising.
Nightheart has appeared only twice and spoken very few lines, but she's a pretty popular character.
Rainswept Flower, for being one of the most genuinely kind and helpful characters in the book, and for having a cool name. She gets tons of fanart.
Lightning Tail, Thunder's best friend and the eventual first deputy of ThunderClan is very popular in certain circles of the fandom.
Fan-Preferred Couple: Tons of shippers were hoping Clear Sky and Petal would become an item, but in the second half of the series Petal dies and Clear Sky becomes mates with Star Flower. It's still a very popular pairing, more than most of Clear Sky's canon pairings.
Some fans admitted to reading The Sun Trail solely because they wanted to see River. Subverted in that he's the only Clan founder that didn't show up until the second book, Thunder Rising. Then fans could enjoy his presence.
Quite a few fans only read the book because of the beginning scenes with the Tribe.
Gray Wing has been shipped with Bright Stream, Turtle Tail, Rainswept Flower, Storm, Tall Shadow, River Ripple, Wind Runner, and Slate. Not bad at all.
Thunder is no slouch, having been paired with Acorn Fur, Lightning Tail, Swift, Flower, Star Flower, Blossom, and his eventual true mate, Violet Dawn.
Moth Flight is actively shipped with Red Claw, Sun Shadow, Spotted Fur, Slash, and Micah, which is pretty decent for someone who was a minor character until her Super Edition, which came out after the arc was over.
Les Yay: There are a surprising number of fans who ship Turtle Tail and Bumble.
"Shaded Moss, actually", Tall Shadow's legendary retort when Moon Shadow sarcastically asks who died and made her leader.
Snake from The First Battle being a Clear Sky fanboy has spread to tumblr. Some◊ examples◊ (mandatory bad art).
One-Scene Wonder: Nightheart showed up, spoke two lines to Gray Wing and Clear Sky, then swam off. A fanbase was born.
Replacement Scrappy: Subverted with Holly. You would think she would be this, being Jagged Peak's actual mate, instead of Rainswept Flower, who died in The First Battle, but the fandom has responded quite well to her prickly personality.
Sacred Cow: The Sun Trail has become one for fans. Bash it at your own risk.
The Scrappy: In The Sun Trail, not a lot of people liked Moon Shadow, because he was a complete idiot and a deadbeat dad.
Ship-to-Ship Combat: The introduction of Star Flower has been taken as a huge blow by the Thunder/Acorn Fur shippers, and a lot of them are getting angry. And what the Thunder/Acorn Fur shippers are going through is nothing compared to what Thunder/Lightning Tail shippers are feeling.
Slow Paced Beginning: It's generally agreed that while The Sun Trail is awesome, it takes a little while to get truly amazing.
In The Blazing Star, Gray Wing gets Ship Tease with Slate after his mate's death because...Slate's hot?
In A Forest Divided, Clear Sky and Star Flower fall in love pretty quickly, especially considering that before the book, they would have been considered a Crack Pairing.
In Path of Stars, Thunder falls in love with Violet almost immediately after he first sees her, and she seems to reciprocate not too long after. However, Thunder does say that he wants to get to know Violet before becoming mates with her.
They Wasted a Perfectly Good Character: One of the complaints the series (specifically A Forest Divided and Path of Stars) faced was that a few of the really interesting characters were never used well.
In The Blazing Star, Petal. Ever since The Sun Trail, she was one of the most interesting characters, had lots of development, and was in the middle of her arc. However, she is suddenly killed during the denouement of the book, and while it does showcase some of her character development, her death contributes absolutely nothing to the story, not bringing about a single bit of character or plot advancement. It especially stings we never get to see the scene where she makes peace with Gray Wing, giving no payoff to her development.
Sun Shadow. The Bonus Scene of The Blazing Star does a good job of setting up his character and the conflicts he'll face when he reaches the forest. He proceeds to do next to nothing in A Forest Divided and Path of Stars.
Snake. He's dramatically introduced in The First Battle, with heavy foreshadowing that he's going to be a major thorn in the side of the heroes later on down the line. Then in The Blazing Star, it comes true, with him turning on Clear Sky at the end, seemingly beginning his time as a major villain. However, he doesn't even appear in A Forest Divided, and when he does return in Path of Stars, it's only as one of Slash's lackeys, a role that could be filled by any cat. His history with Clear Sky is barely even touched on.
Night. She's the first Cat of the Water that the protagonists encounter, she seems like a potential rival in The Sun Trail, and she's River Ripple's closest friend. However, she does all of nothing in the arc, and is lucky if she gets five lines in a book. Her brother gets it even worse, though. He's introduced in Thunder Rising as an enemy of Clear Sky. Then, he never appears again, and the other characters act like he never even existed.
Win Back the Crowd: After the lukewarm reception of The Last Hope and Yellowfang's Secret, The Sun Trail's faster pace and fresh ideas made a lot of fans declare it one of the greatest books in the series. And if it didn't win the crowd back, then The First Battle definitely did.