Here's a question for those who think this is an over reaction and it's not a big deal.
Would you, as a pilot, make the same "joke" transmission and stupid noises over the cabin PA? Or if an official from the CAA was sat in the jump seat?
Unless your answer is 100% honestly "yes" then you should be able to realise what the problem is. And if it is yes, the there's a different problem to address.