When I watch a series, especially with non-human characters, I like to try to guess their size when it isn't said... For Larva, there are many characters, and scenes, even if not every scene a character will look the same size, if we look closely as most scene with other character of similar size, for example, humans, we can guess. The size of our silly Red and Yellow was a long time question, I first though they were very tiny, but then in season one, they looked kinda bigger than in other seasons. But until season 3, their size remained clear to me, due to having more human interactions with different characters than always Tom. So, I personally think Red would be 3 cm/1,18 inches and Yellow 6 cm/2'36 inches. It is mainly based on how they look comapred to human hands/fingers, in Larva Island, there are a lot of clues, except a scene when they looked WAY bigger, like in Change at the end, where Yellow was nearly the size of Chuck's foot when the man wanted to pet the caterpillar, but other times, we can see Yellow being nearly the size of an index finger (which should be something around 7cm/3 inches). As for Red, it's easy, since he's two times smaller than Yellow.
Then, knowing this, some characters can seem very big, or very small for their species, let's take Green, that I thought being an American bullfrog (well they live in New York, USA, so it would be kinda normal) with the many scenes he appears being as big as a foot, but he could be way smaller, when we see Yellow is 2/3 times smaller than his body, which will then question the size of Grey and the Silvers. Grey would then be small for a sewer rat, and even more small the pigeons would look like. But considering they have their fruit peels on their heads, that their moms gave them when they were in nest, would mean they are actually not fully adult pigeons, since the peels can't grow with them. So I still am not sure about them, they didn't even directly interacted with an human being, but with the Larva Rangers episodes of Larva Island, which had some size errors (Booby was the most obvious, as once only his rear ican fit into Green's mouth, and in another scene his whole body fit into the frog's mouth. As for Ivory, he looked like the same size as Green or Grey when he faced them in that episode, and then we see that when he landed on Chuck's face, he was really small, that would make the fusion of the three villain very tiny, like Chuck's head, but considering the Rangers robots are also very small you wonder how all the Larva enter it, then some magical thing may happen, that once either Larva or the villains do their fusion, they get smaller. In the same episode, there's a scene where Green tries to stomp a mudskipper mom and her baby, his foot looked huge, but in another scene he tries to stomp Mango, she looked as big as his foot. Of course, I'm just overlooking ahah, not seriously looking, it's very minor details, but actually fun to compare to me. And sometimes, changing a character's size can be quiet useful, liek shrinking them in a situation to make them look more vulnerable, making them bigger, of course, is the only way to make them seen by the audience when the scene is showing a big part of landscape etc... Anyway, Tuban always do a very great work, and this is why I am a big fan of this franchise! Now I will try to make the size list of some characters, I may be wrong (I am only sure for Red and Yellow), be it's fun to do I think
- Red : 3 cm
- Yellow : 6 cm
- Brown : 4 cm (body)
- Black : 8 cm (body + horn)
- Mango : 2,7 cm
- Pink : 4,5 cm
- Ivory : 6 cm (body)
- Blue : 2 cm
- Cocoa : 3 cm (body)
- Violet : (his lack of appearance in the newer seasons make it hard to compare if it changed, and how he can seem way bigger in some epilogues, but I'd say, 20-25 cm)
- Rainbow : 9 cm (body + eyes, shell around 4 cm)
- Grey : 15 cm (including his big nose)
- Green : (considering he's the oldest villain appearing and that he is the villain the size change the most, it's hard, but comapred to his pals, I'd say 13 cm)
- The Silvers : compared to Grey since they often are around same size, then they would be 16 cm pigeons, but let's say 20 sometimes... Yes, they could really not be fully adult yet, and if you compare them with the regular pigeons, the one that appear in three seasons, especially Hiccup episode, they look way smaller than him)
- Booby : 50 cm (height)
- Clara : 40 cm
- Muscular Mudskipper : 13 cm
- regular mudskippers : 8-10 cm
- Crabsformer/island's crabs : 6 cm (shell)
- Magenta : 3,5 cm (body), yeah, she's big bee! And as a larva, I'd say 8 cm
- Granny bees : look very smol, 1,5-2 cm to me
- Momo : 3 cm
- Mony : 4 cm (she's the biggest/longest to me)
- Mocha : 3,5 cm like Magenta, even if he looks more buffy
- Wasp/Hornet queen : definitively huge, 8 cm at least (body, without her pom-pom/hair)
- Grizzly : 8 cm
- Big Brown : 16 cm (with legs and head, his shell is pretty small, 10 cm or less)
- Tan : 13 cm (his first look, all white and fuzzy uwu), 20 cm when he got a bit older
- Mauve : 30 cm (body)
Well I'll stop there, now you saw my very useless post, bye ;D Next one will maybe be the species identification of the characters!