My husband & I celebrated our 4oth birthdays by inviting 75 of our friends and family to our home.  The theme was a Pajama party. We sent out invitations to a 40th "Pajama" Birthday party. We asked everyone to come in comfy flannels and nothing rude or lacey.  We had the food catered and an awesome dance band. Everyone had so much fun!!!  Mostly because they were so comfortable wearing their P.J.