array behavior

If a field(attribute) in a type is declared to be an array. Then is it always the case that the array will be packed into a single tuple that resides in the database. There is the TOAST mechanism for oversized tuples but that is still considered to be a single tuple. Is there any circumstance in which an attribute which is an array will be broken up into individual
tuples which are somehow associated with the main tuple. Such as if the array happens to have 5000 elements and the tuple will become quite large if these are packed within a single tuple and additionally it may have undesirable performance impact if the queries are not even interested in seeing the array when fetching the object ?

thanks