Like any person with proper breeding, you keep your garden neat. Every year you dress up your garden beds with a fresh layer of mulch. This year, you used bark muck. Then it rained. A revolting sight greeted you the next morning. "Oh, gross! What the #$@* is that stuff?"
Let Grumpy apologize before telling you its name. It's called "dog vomit" -- because, well, that's what it looks like. People with more delicate sensibilities prefer to call it "scrambled eggs fungus." In fact, it's neither a fungus or a mushroom, but a remarkable organism called a slime mold that can actually slowly creep over things. Harmless to people and animals, it appears on decaying organic matter, like bark mulch, feeding on fungi, yeasts, and bacteria. Initially, it resembles a bright yellow amoeba. Then it darkens to brown and releases a cloud of spores that spread in the wind to make copies of itself in decaying matter all around.
Isn't life grand?
I've never seen this disgusting stuff on pine straw, but it frequently shows up in fresh hardwood mulch after a rainy spell. And once the spores get in your mulch, there's nothing you can do. Dousing the mulch with fungicide won't kill them. You can use a shovel to scoop up the nauseating blobs, dump them in a trash bag, and put them out with the trash. But sooner or later when conditions are right, they'll be back. They'll keep returning as long as the mulch decomposes.
So the next time you spot vile yellow goo in your flower bed, don't immediately blame it on Fido. He's only responsible for the mess next to it.