Water off a duck's back

Learned something new today. Again. I used to use the expression "water off a goose". Not the correct one. Even though a duck and a goose have the same type of feathers :) (excuse). Next excuse is that English is not my first language.

I just think it's funny. Some expressions are born out of foreigners not knowing the correct ones. And sometimes it can become really funny.

Like a language I know really well, where a "prick" means a dot. The sentence was ended with a "prick", or please show them to the "whip-room", meaning VIP-room.

More examples, please!

PS. Criticism to a man, water off a duck's back :)