Yerrshers begin their lives as little mushrooms in moist areas such as forests. They are ripped from the ground by Foraging Churses who are looking for actual mushrooms to make soup. Once the mistake has been realized, they are dropped off at the nearest bargain bin, ready to make new lives for themselves. The smallest Yerrshers are called Littlest Yerrshers and can be grown into full sized Yerrshers by leaving them in a cup of water and looking away.

Yerrshers are usually found near a Churse and have a symbiotic Yerrsher-Churse relationship. Yerrshers bring Churses food, and they are rewarded with pats and attenshun.

Yerrshers have a terrible memory, and can't remember where they live. Evenings are like a huge game of musical chairs. Yoshis who forget to board up their houses for the night will sometimes end up with a Yerrsher in their bed.