Cadence is weird, Tia!
Luna hummed quietly to herself as she waited outside the courtyard in a chair two sizes small for Cadence; she was arriving in Canterlot for a short stay, which Luna gladly welcomed. After all, she wasn't able to come by often, being in the crystal empire and all, so any chance to see her pranking buddy was immediately taken. Celestia wouldn't know what hit her, come tomorrow! That is, if Cadence ever showed up. She was thirty minutes behind schedule, and despite enjoying the comfortable chair that she was sitting on (sent to her as a gift from Cadence), she couldn't help but have that nagging thought that something was wrong with it.
Perhaps a problem has risen within her realm, and she is unable to visit today. She mulled over that thought as she munched on the last cookie and drank the last of the milk on the plate that was given to her before ringing a bell, where a servant came out from one of their many hiding places (Luna swore that the servants doubled as the royal spy force), and promptly took the plate away before leaving another plate of cookies and milk for her. Milk and cookies were one of Luna's favorite snack combinations; quick, simple, and it left a warm feeling in her stomach as her nostalgia of older, bygone days returned. After dunking a cookie into the cup of milk, she lifted the cookie to her face, ready to sample its surely mouthwatering flavor, when suddenly, her eyesight was full of a pink pony's face.
"HI AUNTIE LUNA!"
"MOTHER OF FAUST WHAT IN TH-" Luna tipped her chair backwards, and made an attempt to scramble up to her hooves; unfortunately, the chair was firmly stuck to her posterior, and she tried in vain to push it off. Mentally, she made plans for ponies to check her chairs for possible pranks aimed at her posterior from the crystal empire. "Nnngh, don't just stand there laughing at me, Cadence, pull this off!"
Cadence's loud laughter died down to short, soft giggles as she gently tried to pull the chair off from Luna. "Oh, I'm sorry, auntie Lulu! It's just so funny when I popped out like that, and even funnier when I saw the reaction you had after you realized you were stuck in that chair!" It took much force from Cadence, but eventually, with a 'pop', Luna was propelled from the chair, and Cadence was thrown backwards. Both alicorns lay motionless for awhile before slowly getting back up to their hooves, and dusted themselves off before Luna glared at Cadence, who was whistling innocently. Cadence probably did something to the chair personally; after all, it was a chair from the crystal empire made especially for her, so it must have been pranked with something.
"Don't say anything about me getting my rump stuck in a chair, and I won't say how you fell flat on your rump."
"If you say so, auntie! Oh, you have cookies!" A suddenly giddy Cadence reached over for a cookie, and bit into it, enjoying the gushing flavor of cookie-ness it had, a perfectly balanced combination of chocolate, sweet, crispy dough (she never did like soft cookies), and, of course, the most important part of all; the way it left her wanting more of the delectable things. She licked her lips, reaching for another warm cookie, when her hoof was swatted away by Luna, who then put herself between Cadence and the cookies, glaring at her with a sudden coldness.
"What do you think you're doing, Cadence?!"
A hurt Cadence frowned at her aunt's sudden aggression. "I...What? I was eating a cookie, Luna."
"Who eats a cookie like that?"
Cadence was confused by Luna's words, and tried to move around her aunt, only for Luna to follow along with her movement's. "What did I do wrong, auntie Luna?" Cadence was then treated to the most ridiculous reason she had ever heard from anypony.
"You didn't dip the cookie in milk! What kind of pony eats cookies without milk?! It's heresy, I tell you!"
...What? Cadence tilted her head slightly, wondering if her aunt had just taken her medication and was just feeling loopy because of it. It certainly looked like she did. "...I never realized that not dipping a cookie in milk was considered heresy, Luna. I didn't even know there were beliefs and traditions when it came to cookies!" Instead of humoring her aunt about how weird it sounded to be describing cookies dipped in milk as heresy was silly, Luna only nodded, and began on a monologue about cookies, much to Cadence's dismay.
"That is correct, Cadence! Cookies and milk, and milk and cookies! Not just cookies, or just milk, you cannot have one or the other, by my mother's name! Why, the very thought of eating cookies without milk scares me to death, and I pity the poor soul that thinks that they can eat cookies without dipping them in cold, delicious milk! May Faust have mercy on them when it is time for them to be judged of their crimes! If only Celestia saw these things the way I did, then we'd have passed on a law by now that required ALL ponies to dip their cookies in milk! What say you to that, Cadence?!"
"...Well, that was a very interesting speech-"
Ah! She sees my reasoning! "But of course! Should cookies and milk deserve less?!"
Auntie Luna might not take my next bit of news well; I might be a dead princess soon. I'm sorry, Shining Armor! Cadence sighed at her aunt before saying the words that might anger her. "...But I can't drink milk."
Ah ha! This is great this is...Huh? Luna stared dumbfounded at her niece for a moment before the words finally registered with her mind, and she asked the most intelligent question she had. "...What?!"
"I'm lactose intolerant, auntie Lulu. It's a condition that means that I can't drink milk, and there are plenty of ponies that are just like me."
"..."
"Auntie Lulu?"
Luna snorted, and extended her wings out. "A moment, please."
Cadence watched as her aunt Luna took off into the skies, headed towards Celestia's room; idly, she grabbed a cookie, and began to munch on it.
This won't end well. "Oh, she said that, Lulu?" Celestia looked up from the friendship report she had just received from her student (kites, apple juice, a wrecking-ball, cake and Pinkie Pie don't mix well together, apparently), and was listening to her sister complain about Cadence and her apparent disability to dunk cookies into milk.
"Yes, Tia! Why, that is the worst excuse that I've heard from anypony! She even said that other ponies suffered from this as well! That surely had to have been made up on the spot! Cadence is weird, Tia! How can you not dip a cookie into milk?!"
"Well, to answer your question, Lulu, there indeed are ponies that cannot ingest milk, and they are, indeed, called lactose intolerant."
That's impossible though... Frowning, Luna asked a question that was bothering her. "But...Surely she had to have suckled milk from her mother?"
Celestia shook her head, and wrapped her magic around the latest report she was given; after burning up, it was sent to her private archives for her to read later. Her spell left a rather distinct smell of poptarts, which she suddenly had a craving for. I need to work on that spell. "She was given a formula similar to milk that is not milk; many mares use it nowadays, though I think the natural way is the best."
"...Oh."
She'll get a kick out of this... "Do you want to know something weirder, however?"
"What is that, Tia?"
"Her husband, Shining Armor, is much, much weirder..."