I heard this one from a neighbor. She was talking about her husband’s love of gadgets, and that he recently received a new tool that he was crazy about. This is an incongruent conflation of “like a kid in a candy shop” (so excited about something that they behave in a child-like way) and “like a bull in a china shop” (clumsily destructive). The mixup derives from the similar sounding words “china” and “candy”, the word “shop” used in both phrases, and that the two phrases are equal in words and structure (“like a blank in a blank shop”).
This malaphor was written by Michael Gerson in a Washington Post column. https://www.washingtonpost.com/opinions/the-best-fortnight-in-a-decade-for-conservatives-uh-oh/2017/02/06/93e2f1aa-ec9a-11e6-9973-c5efb7ccfb0d_story.html?utm_term=.fe5334ede362
It is a nice mash up of “on the horns of a dilemma” (unable to decide between two things because either could bring bad results) and “bull in a china shop” (clumsily destructive). Mr. Gerson was discussing how Republicans are in a difficult situation, where if they criticize Trump, they could receive massive retaliation. While malaphors are usually unintentional slip ups, this one clearly was not. A big thanks to Sam Edelmann for seeing this one and passing it on!