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!").
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!
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 romancenote which her father,played by Neji, disapproves of 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. Made poignant in the fact that there are no jokes made afterward; just a shot of Tenten, Neji and even the normally energetic Lee quietly looking on at what could have been.