These pictures remind us that when people celebrate, they bring different ideas about everything, and sometimes it can be hard to answer the questions that arise from it. Such as, at what age should the kids stop trick-or-treating.

It can leave parents — and other people contributing to their costumes — feeling a bit torn.

"There's the side where you want your kids to have this wonderful ritual-like festival," Colleen Harmeling, an associate professor in the school of business at Florida State University, told NPR. "But then you're balancing it with these other demands — and those other demands are where morality kind of comes into play."

Harmeling believes Halloween for kids is much more than a sack of candy. "I think it is this visibility to the community that they're embedded in. It's a night of fantasy when they see all of these other kids pretending along with them."

It's like a real-life role-playing game. For millions of kids, it can perform one of the most important functions of play: easing the pressure and stress they're under.

"It's also a moment where they can in some ways break the rules where it's safe," Harmeling explained. "You know, they're wandering in the street. They're among all of these strangers, they're not wearing proper clothes, you know?

So in a sense, it gives them the freedom to be wild.

"That's why it has become such a core rite of passage in our culture because it isn't just candy."

But the benefits don't stop there. The professor thinks that these trick-or-treaters who dress up to celebrate Halloween are doing a service to adults, too.

"They're signaling their appropriate membership in the community," she said. "Like if you are in a high trick-or-treating zone, it's kind of your moral duty to participate, you know, to keep your light on."

As we take part in what is basically a massive candy redistribution scheme, we also get to cultivate our own sense of altruism and feel the warm glow that comes from contributing to our community.

Plus, there's the basic entertainment factor.

"You're witnessing the enjoyment and the emotional contagion of a collective group [of ecstatic children in costumes]," Harmeling said. So there's this shared emotion through all of this."

And if you've ever taken an active part in it, chances are you may have done a double-take at seemingly adult-sized trick-or-treaters. Some towns even ban older kids from it altogether.

According to Harmeling, such actions can be interpreted as both good and bad behavior.

"There's a biological reason behind why you're likely to grab your hand into your bag of candy and throw pounds of it to a three-year-old who's coming to your door, and then offer a single piece to that 13-year-old who's coming to your door," she said.

"It's because they are the more innocent, they're the more vulnerable."

But Harmeling believes teenagers shouldn't feel vilified if they go out to trick-or-treat, and if a child is wavering on whether to go, parents should try to find a way to support them — and make sure Halloween is safe and fun. At the end of the day, they're trying to raise a good person, and it's a great occasion for bonding. So if you believe that some of the kids in this list are too old to be on it, maybe just look away!