Factor 2: Parents who never leave

Mask appeal “I just love it when there’s a superhero jumping around, making the kids scream,” says NYC mom and comedian Judy Gold, star of the one-woman show 25 Questions and coauthor of the new book 25 Questions for a Jewish Mother. “Then the parents ask you to calm them down. Hey, you’re the ones who hired the freak in the costume!”

Once upon a time, moms and dads greeted birthday party invitations with eagerness and anticipation (as opposed to the dread and ennui of today). That little demi-card with an illustration of cartoon pirates saying “Join us for a p-Arrrr-ty!” was, in essence, a gift certificate guaranteeing the adults two hours of free time during which their child would be happily engaged in supervised activity. Today, such an invitation promises parents the thrill of watching two dozen kindergartners take in educational magic tricks performed by Smartsy the Science Clown.

“When I hear that someone’s having a birthday party, I want to stick an ice pick in my eye,” says mom Judy Gold, star of the Off Broadway one-woman show 25 Questions. “Why do I want to sit around and watch kids play games? It’s bad enough I have to do that at my own kids’ parties.”

Loitering parents just add to the number of guests (there’s that need for cavernous venues again) and the quantity of refreshments you’re obliged to buy. Plus, you have to entertain two generations of partygoers simultaneously. Unfortunately, it’s exceedingly difficult to keep pesky parents away.

“We wrote on the invitations, ‘Parents can stay or go—your choice,’ ” explains one Park Slope mother. “I knew from the moment the first mom decided to stay, though, that every other parent was going to stay, too. ”

Her mistake was giving them a choice. When you write out invitations for your next party, be specific. Label it “Kids Only.” List explicit drop-off and pick-up times. And if some neurotic dad is afraid to leave his daughter in your capable hands, let him explain to his little girl why she has to miss out.