mrdreamjeans | Is it a fungal hairball?

OK ... I am going to attempt to describe a substance that I've found in my parents' flower garden twice in the past week. I've never seen anything like it. It is bright neon yellow, the consistancy of oatmeal and was in tennis ball-like form, a large cluster. I first thought it was a mushroom thingie (see, I have a huge vocabulary:), then I thought that it was something a cat, skunk (one lives under their porch), toad or snake threw up; then, when I was planting flowers for Mom yesterday, I noticed that when I dug down into the cypress mulch, there were flecks of neon yellow. Could it be a fungal substance, erupting spontaneously from the ground covering? It's fascinating and gross. Just like some people I know ... Ha! An uninformed, unscientific mind wants to know!

Edit: After receiving some very good feedback, I googled slime mold and found a few photo examples. This one is the closest; but our mass is more condensed and a brighter yellow than in the photo.