Maushold seems to be based on a family of mice. Specifically, based on its white coloration and its Pokédex entries describing how it lives in large nests with dedicated rooms, it may be based on laboratory mice and how they are studied in simulacra of human behavior. Its forms may be based on the concept of a nuclear family, and its doll-like appearance may reference dollhouse figurines such as the Japanese doll line Sylvanian Families.
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It is based on just... mice in general, and mice collectables. Sylvanian Families are little collectable mouse dolls that do, as implied by the name, come in family sets. There is a type of mouse called a house mouse so it is plausible that it comes from that.
I can't find anything about the tail holding from researching mice, but baby mice heavily depend on their mothers in their early stages of development, which could be the source of the clinginess displayed. However, it was likely just a design choice to keep them together.
