1. 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: ___________

Possible meaning: The speaker is referencing John Hancock, who famously signed the Declaration of Independence with a large and prominent signature. The speaker is implying that someone signed their name prominently on the birthday card, potentially taking up a lot of space and leaving no room for others to sign their names.

what is it referencing to

The reference is to John Hancock, one of the Founding Fathers of the United States who signed the Declaration of Independence with a large and bold signature. His name has become synonymous with a prominent and attention-grabbing signature.

and what the possable meaning

The possible meaning of the reference is that someone signed their name on the birthday card in a prominent and attention-grabbing manner, potentially covering a significant portion of the card and leaving little or no space for others to sign their names. The speaker is suggesting that this individual's signature was so large and extensive that it hindered others from adding their own signatures.