mad dog shitting razor blades
When someone is so busy avoiding the actual problem they're talking about they might as well be a dog with a razor blade up its ass.
You: 'Did you steal my pencil?' Them: 'I saw your dog eating my sandwich.'
You: 'Why did you fail the test?' Them: 'I was thinking about my cat's hairball.'
You: 'Why did you skip class?' Them: 'I was arguing with the wall.'