Spooky action at a distance I presume would refer to the sudden reification of a type variable that is established as an existential based on its use in a non-obvious part of the code base. For example, a common one is writing a monadic expression using `do` notation with an existential monad (but not an explicitly typed one) and then one of your monadic actions happens to have a particular type. Suddenly, you'll get a slough of error messages regarding type mismatches, perhaps missing constraints, etc.