What kind of leaf is it on, Iris? And are there aphids around?

It was on some sort of big thistle looking plant. No other critter around.

I am not sure if this shows up, but doesn’t this look almost egg like instead of just coloration?

Yeah, I was looking at those earlier. I was thinking organs. :) DH says it MUST be a Giant swallowtail cat because it looks like a piece of $hit. Oh, I have him so well trained.

The closest thing I could think of is a syrphid fly larvae. Still Googling...

Appear to be a wide variety of syrphids, as their larvae can look very different from one another. Here's one that has similar white dots/coloring, though along the length of its body and not concentrated near mid-body:

I must be related to your husband. Slug/ slug caterpillar looking like bird poop/ dropping were the search terms that came to my mind.

Well, sounds like science experiment time: raise it and see what it turns into. :)

Legs? Slime trail?

I did not see legs or a slime trail in the inch or so it moved. Probably no hope to find and raise it at this point, I look at weeds before I pull and a bit closer after. In this case it was an after, so I looked to find the same kind and put it there.

Shape and the left end in your first photo reminded me of a spittlebug nymph without its bubble "house" Be curious to know what it was.

I like that idea. Is size right and is active spittle in the garden area?

There are no fresh looking nests, but still some rubbery looking residue. I do have adults around.

Looks like a syrphid to me. Some are kinda clear and glossy so you can see their innards. Looks like you can see spiracles and tracheae and stuff?

Any aphids around? Your squishies don't seem to be eating the plants.

Well. Wow. It went all the way from creeping me out to being a really good guy!

I went through the same series of emotions last year when syrphid larvae first appeared on my milkweeds.