Se te ha comido La Lengua el gato.
I know it means "has the cat got your tounge", but sometimes I see it without the "se".
What is the grammar behind that, active vs passive. What I don't like is the "el gato" at the end of the sentence when it is the doer of the action. Comment on that?
RE
Spanish word order is a lot more flexible than English word order. Both versions of the saying are correct. The passive one puts more emphasis on the fact that you are recipient of the imaginary cat's action; the active one puts more emphasis on the role of the cat. You are going to need to let go of the concept of an exact correspondence between any two languages.