These goo monsters originate from a mushroom forest and live in burrows, coexisting with giant spiders. In their chill state goobies are small and spherical, but they can change their form to shape themselves however they want(they can give themselves tails, muzzles, multiple limbs, etc). There's no one goobie look, but the right one is the most common. Mushroom caps and spider silk are popular for goo fashion too lol.

I've been calling them goobies for so long I might end up just calling them that lol. And here's more examples of these guys:
https://www.furaffinity.net/view/41008740/

And an example of how they can look different when they transform:
https://www.furaffinity.net/view/41144339/

The more goos that work together the bigger the creature they can make. They may be small and squishy, but they can wreck some shit when they've got a larger number lol.