Possible Clues:

• NFL championship game in the US
• A pitch with American running back on: for this?
• NFL climax
• Championship game of the US NFL
• 'He's prepared a ___ of popcorn for himself ...'
• With 59-Across, what 18-, 23-, 31-, 37-, and 44-Across are
• Annual championship game of US National Football League
• Feb. 7, 2010, the date of this event's number 55-Across
• Great excuse for a party
• NFL championship game