be off one's beam(VLZ_58); be off one's rocker(What?! Is he off his rocker? -- Он что, спятил / свихнулся?ART Vancouver); go bananas(о животных; в прош. вр.: 'We were on one side of the creek, the creature on the other and our horses went crazy. Roger's little horse just went bananas.' (Bob Gimlin in an interview to Seattle Post, 1985) -- Лошадка Роджера точно свихнуласьART Vancouver)