I wonder whether this idiom was used in reallife: Slip on a banana skin / 'Slip on a banana peel' Could anyone clarify me?
Yes. It's a very common device used in slapstick comedy. However, believe it or not, I actually saw a person slip on a banana peel and fall down in real life! My mom and I were dining in a restaurant, and our table was next to a window that overlooked the sidewalk. Mom had just finished saying "Look, some slob threw a banana peel on the sidewalk" when a pedestrian passing by stepped on it, slid and fell to his knees. I know it's inappropriate to laugh at someone's misfortune, but we were in hysterics.