The cat is for the endings and it's spot is different in each ending due to each ending being different. For endings 1-4 the cat is in the particular location the ending takes place in (town for 1 by the derelict building, The castle location for 2 in the bottom left just outside the battlements, The throne room for 3 on the left side, just above Rudolf, The courtyard for 4 in the top right of the courtyard itself) For Ending 5 the cat is on the top of the castle. Go outside to the upper level Where Ema and Tonkin are, climb the ladder and the cat is at the top right.