Maybe there is no nictatating membrane and 10 year old Stinkfly just has his eye stalks hidden too far inside and we can't see the pupils.

He is the only version of Stinkfly with his eyes inside his stalks after all. The rest have them on top for some reason

Theory on the slime’s changing properties.
Each eyestalk has multiple chambers that release a different mixture of fluids. Making the slime sticky, slippery, flammable, etc.

One of many things I love about being a Ben 10 fan is that we head canon the shit out something so simple. And I also thought of the Omnitrix as a cyclops eye as a child. You're not alone.

The celestialsapiens Just decided to Give stinkfly Pupils for no reason.

I didn't think his face badge was an eye but I used to think his eyestocks were mouths if that counts.

When I watched this video and you mentioned how Stinkfly tail works close to human legs I created a theory. Maybe in the past leopterans had one more pair of legs but slowly that pair fused together creating their tails.

I had a theory that maybe the reason why Stinkfly as 10 year old dosent have pupils is becouse  leopterans shed their exoskeleton the same way how crabs or snakes shed and when leapoterans are 10 years old they shed but it takes some time to completly get new carapace so until then their eyes get more dim and less see thru just like in sankes.

BABE! WAKE UP, OLLIE IS IN HER BAG AGAIN!

As someone who also kinda takes issue with the data dump, i actually think it can be explained really easily: it doesn't give Ben the immediate knowledge of the powers, but rather, "downloads" the innate instinct of the species into his brain. So, it comes naturally for him, but he isn't exactly aware of it, that's why he still needs to learn in some cases (this could also play into stuff like him controlling Stinkfly's tail like he controls his legs, the movement might come naturally for him like the movement of his leg). More complicated abilities might take more thought or experience to figure out (which would also explain why Ben still doesn't seem to know every ability his aliens have, ex: Chromastone, AmpFibian, Toepick, Terraspin and such). Take birds for example, flying is innate and instinctual to them, but they still need time to practice and fully figure it out.

I think the Omnitrix is just kinda changing stinkfly's DNA so he has pupils to make him seem a bit more human kinda like how almost all the aliens in omniverse look a little humanized.

2:20 That is a big reason why I prefer pupils

How did I never take note of this inconsistency before 😅

another thing on the membrane is that in the reboot Stinkfly's eyes are designed like googles meaning they could serve a similar purpose.
I know reboot Stinkfly is basically an entirely different alien but it is interesting that if this theory is true they'd both share that one design detail

0:40 fun fact diesel is technically flammable, but it puts out fires because the fumes are so strong. No oxygen is allowed to go in but if you put diesel on something that is flammable, the flammable thing catches fire first and allows a fire to go on long enough to catch the diesel on fire, I believe that’s what’s happening with stink flies goo

Guys. Peak is here.

Well that's interesting to know also 0:49 vilgax is much more larger than stinkfly and has armour on so he has to be really heavy even if he manage to keep him airborne for a few seconds it's still impressive

1 I love this peak content, Stinkfly is underrated
2 Theory about the chemical inaccuracy:

I think Kevin 11, having way weaker Stinkfly abilities than OG Stinkfly, might have dilited, oxidised slime. Let's say it's partially white phosphorus.
Normal slime might have such density that the phosphorus doesn't get the oxygen to incinerate, but Kevins diluted one might be so thin it oxidises.

I think it’s all an age thing based on both the lepodotrian prisoner from SOTO and 10K’s Stinkfly, a stylistic change, and because people keep confusing the Omnitrix symbol with being his eye

2:30
ALL OF US TOUGHT IT WAS

Specially when the damn eyes are not looking where they should

2:24  I honestly kinda like it if it was treated like that like the dial twisting to make it looks like it zooms in is cool af