I think you need to change the rating to at least a T. Otherwise, this is a cool parody.

TLDR; a very good pilot that balances the grossness well, hoping for more character based interactions.

I don't know whether I should be relieved or disappointed in the conservative use of gross-out scenes. However, I think the ones that were there were used tastefully and didn't have a lot of focus placed on them, allowing for the one that I found truly disgusting to be more effective. I also appreciate that the grossness of the setting is used more as a backdrop or one component for the humor, instead of it entirely being gross-out humor (I also appreciate all of the characters having their own limits toward acceptable grossness, it fleshes them out).

I do wish there was more character interactions, but I'll chalk that up to this being a pilot that's just introducing the premise instead of as a standalone thing. I do hope that Pickle's romanceing attempts aren't as much of a focus later, or at least isn't the entire basis for the dynamic between him and Dill.

The first thing that should be done is making your collision more reliable. This can probably be achieved by starting with simple shapes and consistent sprite sizes. Also, it'd be more fitting if the ground and blue enemies were custom assets like the character and flies. This won't garuntee that it'll be good, but it will clearly indicate that care was put into it.
I used GDevelop once, so I understand how much of a pain it can be to do things.

I really like this! The fact that there aren't any bushes in the first place is definitely my favorite part, but I also appreciate how you were able to convey the character emotions within the bounds of their original designs (I don't know if this is impressive or not, just something I think I had trouble with at one point). The framing of the scenes are also pretty good.
Outside of general refinement of your style, the only real suggestions I'd make is 1) having the close-up of Undyne grabbing Napstablook be from the front (so the arm is obscured) to better lead into the next panel, and 2) spacing out the final panels (Alphys in the restaurant and the impact) so there's more anticipation between the panels. You don't even have to expand the scenes that much, you could just make another page and leave the empty space empty.
For the "refining your style" part, I've heard that studies are the go to, and I'd suggest limbs and how they interact with perspective.

It reminds me of the Link and Zelda dynamics. I would like to know what Curly's saying, though...

This feels very serence and comfy, and I think it might be better if the hills in the background were replaced with more sky.