It was Halloween night in 2012 and James and Lily had just returned home from Trick or Treating.

Albus, who didn't have much a sweet tooth, had chosen to go to a haunted house with Ginny while Harry took James and Lily Trick or Treating.

James was wearing the Darth Vader costume he'd trick or treated in and Lily was wearing the Budweiser bottle costume she'd trick or treated in.

Both James and Lily were carrying reusable plastic Jack O Lanterns they'd used to collect their candy in.

"Hey James, " offered Lily, "Would you like to trade candy with me? I know we both have vastly different tastes in candy so I'm thinking if we trade, we'll both up with a haul we like better."

"That's a great idea Lily, " answered James instantly "You can come up to my room and we can trade in there."

"Alright then, " said Lily brightly and she followed James up to James's room.

"So, how should we go about this sis, any ideas on how to execute our gameplan?' inquired James.

"Let's each dump our candy onto one side of your bed so that we can see what we've got and then I'll let you make the first offer, " responded Lily.

Next nanosecond, James dumped his candy onto the left side of his bed and Lily dumped her candy onto the right side of James's bed.

"So, Lily, " started James, "I know you're a huge tropical girl."

"Hear hear!" beamed Lily, "Tropical flavors put me in a soothed and relaxed mood. It isn't even about the specific flavors but the general tropical experience for me."

"Well," continued James, "I'm a bold boy and I LOVE berry flavors. The intensity of berry flavors feels like exactly who I am. Therefore, my first proposal is this: I'll trade you my bag of Tropical Skittles for your bag of Wild Berry Skittles."

"It's a deal, " said Lily glowingly.

James picked up his pack of Tropical Skittles and Lily picked up her pack of Wild Berry Skittles and they reached out hands and made the trade.

Once the trade was complete, James and Lily each put their newly acquired candy into their plastic Jack O Lanterns so that there could be no confusion about what had and had not been dealt with. They would do this after each trade.

"Thanks, a lot, Lily, " smiled James, ""The intensity of Skittles is really overrated though. Starbursts are way more intense. Though I suppose that makes sense when you think about how much bigger a starburst is than a skittle."

"You don't eat Skittles the right way, " Lily told James, "They're not meant to be eaten one at a time. They're meant to be eaten in handfuls. Next time you eat Skittles, try popping three or four in your mouth at once and the intensity will meet your expectations. Starbursts ARE more intense, but your disappointment in the supposed lack of intensity of Skittles is the result of you not eating them the way they are meant to be eaten. Speaking of Starbursts, let's make that same tropical/berry swap with those."

And they did.

"Now, " suggested James, "I love candies with nuts in them whereas I hate creamy stuff. Just the way my taste buds developed I suppose."

"I'm the opposite, " grinned Lily, "I hate nuts, but I love anything creamy. It's weird in a way because I love peanut butter but loathe peanuts whereas you despise peanut butter but savor peanuts."

"So that provides a perfect opportunity, " beamed James, "Lily, I'll swap my Peanut Butter M&Ms for your Peanut M&Ms.'

"James, that works out perfectly, " said Lily cheerfully.

Both James's and Lily's eyes glowed as they exchanged M&Ms.

"Hey, James, " offered Lily, "Since you like nuts and I don't, why we barter Hershey's bars. I'll take your plain Hershey's bar and give you my Hershey's with Almonds bar."

"Offer accepted, " replied James, "I do like the plain Hershey's bar, but the opportunity cost of giving up my plain Hershey's bar is an opportunity cost I'm perfectly happy to pay to acquire an extra Hershey's with Almonds bar. Man, I LOVE Hershey's with Almonds."

So, they made the switch.

"Well, Lily, " piped up James eagerly, "My favorite candy is Snickers. Since you don't like nuts, you can't like Snickers, since Snickers have peanuts in them."

"Too true, mate, " replied Lily.

"For some reason, maybe I don't care for fluff, but 3 Musketeers bars don't do it for me, " said James briskly, "I'll peddle you my 3 Musketeers bar if you'll peddle me your Snickers bar."

"Let's do it, " said Lily happily, "3 Musketeers is my favorite candy so we're doing a my favorite for your favorite swap. "

James tossed Lily the 3 Musketeers Bar while Lily tossed him the Snickers bar.

They went on trading candy for a while until they each had two pieces of candy untouched in their original piles. One of the candies was Reese's Peanut Butter Cups and the other was Payday bars.

"This move is obvious, " smirked Lily and they made the obvious trade a nanosecond later.

Once the candy was all off the bed and James and Lily both had full buckets again, they just smiled at each other for a minute.

"James, " said Lily sincerely a minute later, "Thank you for trading with me.'

"No problem, Lils, " said James cheerfully, "Trading candies was fun and we both ended up with better hauls because of it."

"Bingo!" grinned Lily.