Today Denny's ran a promotion offering free Grand Slam breakfasts to all customers from 6am to 2pm. A couple friends and I took part in the festive activities and enjoyed a great deal (and with only a 30 minute wait or so).
I was surprised at some of the customers' questions and actions. Many assumed that the whole breakfast was free, and were shocked when they were given a bill for their coffee or orange juice. I overheard another man clarify with the waiter whether the 3 glasses of milk his table just ordered were free or not. And another patron was actually walking out the front door until a manager yelled at him to stop and pay his bill, to which he reluctantly agreed to do.

When I heard "free grand slams at Denny's" I immediately wondered what the catch was and what I would have to buy in order to get the deal. Apparently others heard the same phrase and immediately assumed that not only was there no catch, but everything at Denny's that morning was on the house.