Before someone asks why there isn’t insane inflation from banks printing an infinite amount of money for themselves, the Hong Kong dollar is pegged to the US dollar. In order to be allowed to print HKD, banks must have an equivalent amount of USD on deposit.
My favourite is the Royal Bank fiver with mackerel on one side and Nan Shepherd on the other. Apparently there are clouds of midges that only show under UV light, but I’ve never had a UV light and and an RBS fiver at the same time to check.