In the play Dinner for One, James the butler says, "I'll kill that cat," at time 14:05. What does this mean? Is he referring to the tiger rug which keeps tripping him, or is it a saying or colloqualism?
According to wikipedia, the "cat" reference is a consequence of drinking the water the flowers were standing in. That is, James has approached Mr. Winterbottom's chair; by mistake he picks up the cup with flowers, pitches them away, and drinks the water. The reference mentioned above comments:
Schließlich zeigt er unzählige Varianten des Einschenkens und trinkt versehentlich aus der Blumenvase statt aus dem Becher, was er mit einem deutlichen Verziehen des Gesichts und der Bemerkung “I’ll kill that cat!” quittiert (sinngemäß: „das schmeckt wie Katzenurin“)
which (in effect) says that after numerous variants of mis-pourings, he drinks by mistake from the vase rather than the cup, then with significant facial distortion exclaims, "I'll kill that cat!" – with implication, "this tastes like cat pee".
Comes from a time when cats were less loved and kept more for practical purposes (catching mice) and were blamed or used as a scapegoat (Sündenbock) for any otherwise inexplicable minor bad surprise, the expression became common and was used even when there was no possibility that a cat could have been the cause.