Denny's is one of the only restaurants open 24 hours a day even on Christmas, it's the place where teenagers go to drink coffee and eat french fries for hours, and in keeping with the American diner tradition Denny's is always affordable.
What started out as a donut shop called Danny's Donuts that opened in Lakewood, California back in 1953 has grown to become Denny's- one of the largest and most successful restaurant chains in American history:
The 24-hour doughnut shop grew quickly, expanding to a larger menu and roughly 20 locations by 1959, and changing its name to Danny’s Coffee Shops along the way. But the founders worried that the mini-chain was at risk of getting confused with nearby Coffee Dan’s, so they switched one letter to create the Denny’s we know today.
The Grand Slam Breakfast debuted in Atlanta in 1977 with a name inspired by legendary baseball player Hank Aaron, and the Grand Slam has been about the same price my entire life- which is probably why it's Denny's most popular dish.
When Denny's says they're "always open" they mean it, and their 24-365 status almost became an issue when most of the restaurants decided to close for Christmas back in 1988:
When almost all the Denny’s locations closed for Christmas Day in 1988, many stores realized that they didn’t have any keys, or even locks, since they never used them. All told, 700 of the 1221 restaurants needed to get new locks installed for the holiday.