I saw this singing busker in the underpass at Green Park Tube the other day, who clearly thought that wearing a Santa hat rather than is normal hat (seen propped on an amplifier) would be a way to bring in the coins. He was right as a number of people stopped to give him cash.
This following two busking Santas from a few years back still remain my personal favourites. The first as he was hugely enthusiastic.
And this one because a busking Henry Hoover with a Santa hat on is weird even for the Tube