We have had extra people numerous time and never had a problem. One time we had 7 people in a 4-person 1 bedroom room - that was too crowded) But Worldmark strictly enforces the person limit and has you write down the number of people in the room.

I think the only way you would have a problem is if a grumpy old couple was in the room next to you and counted how many people were in the room and then made a complaint.