Neil blinked. “Have you ever actually gotten drunk?” he asked.
“No, my duties did not allow for overdue consumption of drinks,” she replied. “And I never liked the taste, anyway.”
“Then that’s why you don’t understand,” he insisted. “It has to be experienced to be understood, Luna.” The offered beer jabbed itself forwards, and he placed it in her folded hooves. “Just let free for the night. Things’ll be serious enough tomorrow.”
She looked down with a frown. “I don’t believe I’ll…” In one fell motion, her horn glowed, the cap popped off, and the bottle deposited itself in her mouth. Reflexively, she swallowed, before grabbing it out of her mouth with a gasp.
“What was that?” she demanded. The Nightmare just laughed maniacally.
“I know the real reason you don’t imbibe,” it hissed smugly. “Any second now…”
Luna’s eyes widened, then shrunk to pinpricks. “Oh my.”
Then, without any fanfare, her eyes rolled up in her head and were promptly replaced by the Nightmare’s gleeful ones. “Heh,” she chuckled. “You poor souls stuck in bodies are so weak, aren’t you?”
Neil blinked muzzily. “What did you do?” he asked.
“Alcohol doesn’t mix well with magic. For the usual magic-user, it just means they can’t hold their liquor. But for an alicorn like moonbutt here, the stuff screws up stuff big-time almost instantly. It’s like a tranquilizer, so I made her gulp a bottle of the stuff. She’s so drunk and woozy it was child’s play to take over.” She snickered. “Ironically, now that I’m not fighting her directly, it’s much easier to take over.”
She attempted to go somewhere, but she stumbled and swayed so badly Neil couldn’t tell what direction she’d intended to go. Several tries only resulted in her successfully slamming facefirst into the wall before slumping against it.
“Why are these hooves so clumsy?” she lamented with a frown.
“Well,” Neil guessed, “If Luna’s drunk, you’re sharing bodies, right?”
“Yes, but I… oh.” Hoof tried to meet face, but ended up missing by several inches, and the overbalance deposited the Nightmare on her rump.
“So I think you’re drunk, too.”
“I am a Nightmare!” she flared, stumbling to her feet. “I am beyond pitiful things like being drunk…” She tottered, only barely catching herself. “I cannot express my disgust with this pitiful sack of flesh adequately in any language.”
Luna’s voice slurred out, “Serves you right, you sneaky parasite.”
The Nightmare snarled, “Shut up!” and punched herself in the mouth. Then, she blinked, temporarily slightly more lucid from the pain. “…I’m not just drunk. I’m completely wasted. My superior mind has reverted to assaulting my own body. I’m going to save myself the embarrassment.”
The cat’s-eyes fled, replaced by normal pupils, as Luna (still drunk) returned to dominance. “That sneaky little creature,” she mumbled. “Get back here so I can yell at you for getting me drunk!”
Neil suddenly found he couldn’t stop laughing as Luna began to rap on her own head in retaliation. He solved that problem by downing another drink.
https://www.fimfiction.net/story/235739/4/accommodations/chapter-iv-a-drink-is-had-and-news-is-made