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.
Also, the OP (both versionsnote There's also an English version without Hironobu Kageyama, and just Animatal USA.), and the second ED for that matternote "Lee, Lee, Lee, Lee, Rock Lee! Ninjutsu muri, demo shinobi!..."...
Ensemble Darkhorse: Sasuke's status as this is lampshaded in the popularity contest (ranking #1) and the episode title where he finally gets the spotlight ("The Shinobi You've Been Waiting For!").
Heartwarming In Hindsight: After Hinata beats Hanabi in Chapter 34, Hiashi praises the both of them, and says that the Hyuuga's future is bright. At the end of the original series, Hinata married Naruto and had two children, continuing the Hyuuga clan.
In one of Lee's skits in Episode 35-B he suggests that Hinata gives Naruto a handmade scarf as a gift but Tenten dismisses the idea. This is one of the key events that actually help begin their relationship in the last movie.
Hilarious in Hindsight: The series has so many of these moments now that Naruto has ended that it's not a stretch to wonder if Kenji Taira was trying to retroactively spoil it for the fanbase. The fact that he was an assistant to Kishimoto doesn't help either.
In Episode 35-B everyone gets codenames at one point. Kiba and Akamaru get Mittens and Boots, which are clearly cat-related names. When Tenten points that out to them, Kiba says "We don't discriminate in our home." At the end of the main series, Kiba can be seen flirting with Tamaki, the cat-obsessed girl from the Uchiha Secret Hideout.
Every instance of Neji being overprotective towards Hinata.
Played for Laughs when Sai asks whether Lee has a penis and Lee promptly answers that he does and drops his pants.
Sai (stunned): Th... This is indeed the beautiful blue beast of Konoha!"
When the Narrator reveals Lee's most embarrassing secrets in Episode 33B, he mentions that the reason why Neji is a girl in a lot of Lee's skits is because Lee finds it to be cute. Make of that what you will.
Episode 25-A, when Team Guy notices that the middle character on Gaara's forehead has changed from “Love” to “Romance”. Lee deduces that the person who Gaara has a crush on is...Neji, the former falling for him while he was once again Dragged into Drag by Lee.
Episode 40-B takes it to new levels, where in order to see if he's suitable for Hinata, Neji trains Naruto by making Naruto take him on a date. And then Hinata recognizes him as a rival in love!
In an early episode, Lee, Neji and Tenten dress up as if they were a family. Neji and Tenten are the children, Lee is the mother. While Guy isn't present at this point, it's implied by their conversation that he's supposed to be the father.
Idiot Plot: Even for the sake of comedy taken into note, chapter 35's problem would have been easily resolved if Tsunade had just done a shadow clone jutsu so she could " be in two places at one time". And even if she wanted someone to take her place, as her "lesson" with Sakura shows, Tenten was probably the worst person she could have chose to replace her.
Orochimaru gives up against Tenten after being hit with paper fans. And he had just pointed out that Tsunade not being in the village and everyone else being kept at bay by Tenten's orders would be the perfect time for him to strike.
Les Yay: Tenten wins the "Mr. Leaf" contest despite being female. Even though Tsunade explains why (she protected Tsunade from the other contestants when they got a bit too Hot-Blooded), it's unavoidable. Tenten's Hero-Worshipper tendencies regarding Tsunade don't help either.
The Love Bugs drama in Episode 42-A, where Hinata plays a schoolgirl who has a romance with a boy that saves her from gangsters...and Tenten is the one who acts as the boy.
When the girls all visit an onsen together, dialogue from off-screen suggests that Ino at some point grabs Sakura's breasts.
One-Scene Wonder: Mild example. "Male Tenten" shows up briefly in the second half of Episode 3, yet has a good amount of fan art and fanfiction.
Tear Jerker: Chapter 33. It's more like a somewhat sad moment than a full-blown Tear Jerker, but due to some Easy Amnesia, the only thing that Sasuke and Itachi can recall is how they used to be good brothers before everything went to hell...and they promptly act like such. While hilarity still ensues, Lee notes that Sasuke and Itachi are genuinely having fun and Neji notes that maybe if things had been a little different, perhaps they could be like this all the time. Apparently even a gag manga like this couldn't make light about such a tragic backstory, as there's just a shot of Tenten, Neji and Lee quietly looking on at what could have been.