It sounds like one of those classic “natural mysteries” where you initially imagine tiny aliens or lost Styrofoam balls, until you learn the fascinating truth.

What surprised you so much in the woods was most likely one of these two:

Yellow Slime Mold (also called “Witch Butter”)
Although it looks like a mushroom, it’s actually a slime mold (Fuligo septica). Surprise: This thing is neither a fungus nor a plant—it’s a single-celled organism that can walk.

Why it’s surprising: Slime molds can move (very slowly) to find food. If you returned the next day, the yellow ball might have moved a few centimeters.

Appearance: Initially bright yellow, foamy clumps that later solidify into a firmer, dusty mass.

Gall wasp intestines (gall apples)
They may also have been perfectly shaped, yellowish-red balls on the underside of oak leaves or on the ground.

Surprise: This is not a growth of a tree, but a dwelling. The gall wasp laid its eggs in the leaf tissue, and the tree was essentially “tricked” into building this protective capsule for the larva.

Contents: If you were to (carefully) open it, you would find a small larva inside.

Pea mushroom (young)
In its very early stages, some gasteroid mushrooms can peek out of the ground as small, yellowish balls.
Surprise: When ripe, they often look like dried dog poop or dark lumps, but are known among gourmets as “Czech truffles” (although they are more commonly used to color sauces).

What surprised you so much? Did the “thing” move or did you discover something alive inside?