What happens when a friend emails me a photo of an unusual fungus found in one of your houseplants? They can expect to see it shortly thereafter in knitted form, of course! This is the yellow house plant fungus (yes, let's be descriptive as possible, shall we, taxonomists?) and it will often grow in inoculated potting soil that stays moist... which a lot of indoor plants don't like anyway... so maybe let it dry out a little bit and see what happens. They are not harmful to the plant itself though; just don't make a stir fry with them as they are toxic.
This structure was knitted as part of my 52 Forms of Fungi project, through which I will knit a different type of fungi for every week of 2013. Check out more of the forms from this project.