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.
G-Rated Sex: Possibly. As they're preparing to leave the secret cave Gabu hides them both in during the wolf attack, the pair's conversation turns to the full moon and how much they simply enjoy being with each other. It gets quite emotional, and the camera pans away as they decide to skip going home and just spend the night in the cave together.
Controversy exists over the homoerotic overtones of the anime. Word of God confirmed that, in actuality, Mei was always intended to be a male character, but was written in the children's books as gender-ambiguous so that he'd appeal as much if he were female as if he were male. The film merely restored that gender specificity.
Viewer Gender Confusion: That incredibly adorable, doe-eyed goat who sports a pink scarf and has a deep friendship with a male wolf is a boy. It's especially noticeable due to his masculine voice.
The Woobie: Mei is just so gosh darn cute when he's being terrified.
Gabu as well, being teased by the other wolves as a pup, and that his punishment for saving Mei is to spend the night in a dry well. He is definitely this when Mei tells him that the only option for either of them to survive is for Gabu to eat him. Gabu completely breaks down weeping, and when he leaves the burrow, he starts searching for grass to feed Mei, hinting that he'd rather starve to death than do it.