Wasn't sure if the mushroom category includes things lichen and fungi.

These Pixie Cup lichens are around 2 cm in height, and procure nourishment via a symbiotic relationship with a fungi, with perhaps a third contributor as well. While reading about this, I came across this naturalists jingle...

"There once was a young woman living in the woods who was a great cook. Her name is Alice Algae. She lived in a run-down house and had no money to fix it up. One day, a gentleman called Freddy Fungus came along. Freddy was very handy with tools and offered to fix up Alice's house in exchange for some of her fine cooking. They agree and Freddy repairs the house and Alice feeds Freddy daily while he works. After a short time they both realize that this is a good situation and should last longer. As the story goes, Alice Algae and Freddy Fungus took a "lichen" to each other and lived happily ever after."