United States pizza franchise Little Caesars may be regretting a promotion it did for the NCAA's March Madness tournament.

The pizza chain tweeted this week that if a number 16 seed beat a number one seed, everyone in the United States would get a free lunch combo April 2.

It seemed a pretty safe idea considering top-ranked teams were 135-0 against such opponents going into Friday's games.

Then UMBC happened.

The University of Maryland Baltimore County defeated number one seed Virginia 74-54 to become the first number 16 seed to upset the odds, and Little Caesars tweeted after the game it will honour the promotion.

The company posted: "Because 'CRAZY HAPPENED' with a #16 beating a #1 (!!!!), everyone in America gets a free #LittleCeasars Lunch Combo on Monday, April 2nd."

The lunch combo includes a four-slice deep dish pepperoni pizza and a 20-ounce drink.

Something tells us there will be long lines at Little Caesars locations on April 2.