Not only is the 24-hour joint that gave America the Grand Slam breakfast and a grilled cheese sandwich filled with mozzarella sticks open on Christmas, but the holiday is the chain's busiest day of the year. According to a Denny's representative, 1,236,633 diners filled Denny's booths on Christmas Day last year, with most popping in between 10 a.m. and 2 p.m. Those customers aren't waiting for the waitress to carve them off a slice of ham or turkey, either; 233,812 Build Your Own Grand Slam meals were served last Christmas, making it the holiday's top seller. In Denny's defense, the Build Your Own Grand Slam does get dressed up a bit for the holiday. This season's options include bread pudding french toast with a sweet cream glaze, brown sugar ham steak and pumpkin pie pancakes. The rest of the menu gets into the spirit as well by offering a holiday turkey dinner with turkey breast, stuffing, gravy, cranberry sauce and a choice of two sides and holiday turkey melt sandwich with turkey breast and stuffing topped with melted swiss, served with a shmear of cranberry honey mustard spread and a cup of turkey gravy for dipping. It's not exactly Norman Rockwell's idea of a holiday at the dining room table, but you can always get your Red Velvet Pancake Puppies with cream cheese to go.