As I’ve said before, some anime like to have things so big that the square/cube law says they shouldn’t be able to support their own weight. But weight only applies when there’s gravity, right? So how about giants in space?
Transformers Energon was the terrible English dub of Transformers Superlink, which wasn’t that good to begin with. One infamous line of dialogue from it was “We warped into another galaxy on the outer reaches of the solar system.”.
That’s an extreme example of an issue that a lot of other anime have to a lesser degree; mixing up astronomical terms and/or the scale associated with them. Several series have used “galaxy” like it meant “universe”. Others don’t seem to realize how close a “moon” and a “planet” can be in scale.
This is a topic that was already well-covered in The Physics of Superheroes. But while The Atom and Ant-Man/Giant-Man/Too-Many-Names-Man have size changing as their explicit super power, a lot of anime (and near-anime) characters do it incidentally, as a part of other transformations. Of course, so does the Hulk.
For example, Devilman is considerably taller as the demon Amon than as the human Akira. (Or in Mazinger Z vs. Devilman, much taller.) Well, at least he’s supernatural.
A lot of anime like to have things big.
The very first super robot, Tetsujin 28, is 18 meters tall, big enough that it’s English name was Gigantor. Of course, a lot of other mecha (especially the less realistic ones) are even bigger; Zearth from Bokurano is 500 meters tall. But it’s not just mecha; Dragon Ball, One Piece, Naruto, and Attack on Titan are just some of the more obvious examples of anime with giant creatures of one kind or another.
I saw this video in Japanese a while back, but now YouTube user MetroidSuperFan has translated it into English. It shows size comparisons of a lot of mecha, robots both real and fictional, astronomical objects (the mecha get really big), and various other objects for reference.