I hoped to sign the birthday card our team bought for Coach, but I couldn’t find a spot to sign my name because someone went all John Hancock on it and signed his name across the whole card.
Reference to:______________________________________________
Possible meaning: _____________________________________________
Reference to: John Hancock (American statesman and Founding Father who famously signed his name prominently on the United States Declaration of Independence)
Possible meaning: The phrase "went all John Hancock" means that someone signed their name in a bold, prominent, and possibly excessive manner. In this context, it implies that someone signed their name across the entire birthday card, taking up all available space and leaving no room for others to sign.