Saw this ad at superbowl yesterday and DH went crazy
I just called my nearby Denny's and asked if there's any restrictions. The Manager said nope asides from it's for dine in only. He warned that there might be long wait for tables tomorrow but if there're 4 people in your family coming, they will give you 4 grand slams between 6 am to 2 pm.
I did not ask if you could have seconds servings though ;p maybe no.