Using Values Array from Custom List In a formula

I’ve never tried this, but these possibilities occurred to me

1. Create a hidden field (prefaced by two underscores) that hold a hard-coded list of values and use the ruby script to interact with it like the array. Don’t know enough about Ruby to suggest syntax, but conceptually, it should be doable.
2. Create a Function in Mockaroo - Function editor that returns the array you’re looking to use and call that from the field’s formula