banana peel: the skin of a banana (especially when it is stripped off and discarded); "he slipped on a banana skin and almost fell"
If an important or famous person slips on a banana skin, they say or do something that makes them look stupid and causes them problems. waiting for the government to slip on this week's banana skin. an embarrassing mistake made by someone in a public position, especially a politician or someone in a government American Equivalent: banana peel