The unknown or otherwise unseen people that typically live in a form of cubby-hole found in areas such as band halls, gymnastic centers, and other places of mass gathering that has a sense of trust to its community. These people are a quick excuse as to why something in a cubbie goes "missing."
Also, these people can also be considered people who practically live where their cubbies are.
"Jan, what happened to that sandwich you were keeping with your jacket?"
"Must have been those cubbiehobbits...."