Depending on the campground and you you do one of the following:
1: Park elsewhere
2: pay a small additional charge for the extra 2 bodies (This is to offset the cost of additional water,sewer,electricity,trash pickup)
3: Manager says "OK" no problem
and 4:
I watched a family..like 7,,Pull into a state park like 8 or 9 pm (After the office closed) They all used the shower and other facilities and by 7:30 am were gone..... Office opens a 9
So they camped for free.... Tell they got home and the police knocked on their door.. Defrauding the state is a serious offense don't you know.
(Manager came in before sun-up and inventoried the park taking down license plates... Once every pulled in at night registred he sent the remaining plate to my employer (State Police) and.. Well).