In this talk I argue that in Spanish there is a type construction, involving a verb with the unaccusative se clitic and a dative, where the dative is in fact the external argument, which renders the construction comparable to a transitive structure (in the well-established unaccusative-transitive alternation). A number a tests and criteria are reviewed to support the external argument status of the dative (which in fact can be assimilated to the status of locatives and datives with some impersonal verbs, see Fernández Soriano 1999). These are: unmarked word order, raising and binding. On the other hand, there is also evidence for the non externalized status of other, internal, argument: impossibility of anaphor binding, possibility of being a bare NP, inability to control, among others. I conclude that in this constructions the dative is an instance of quirky case.