Mad as cheese
I was delighted to find this wee man on the back of a greetings card. Years ago, as huge big Breakfast fans, we went to see Mark Little at the Assembly Rooms in Edinburgh during the Fringe. A surreal evening ensued. If you don't know who he is, then the phrase "Bouncer's dead, lady!" will have no relevance. A lady in the audience persisted in asking him where Bouncer* was.
For some improv Mark asked the audience what he was as mad as. Same lady came back with "Cheese"...... it's been a staple in our house ever since.
* Bouncer was the dog in Neighbours when ML played Joe Mangel. Bouncer has long since trotted off to the great kennel in the sky.