It's a short story I wrote one day after eating a reese's cup while listening to a lecture on Charles Darwin and Voyage of the Beagle.
Don’t touch those; they’re to feed the specimens in the vivarium!” Darwiz growled at the captain of the small space brig. The purple alien’s body possessed an extremely high concentration of oxygen, allowing the creature to absorb organic molecules through the skin and digest the particles rapidly without the cumbersome respiratory and digestive systems of lesser beings.
Captain Fitzrog scowled and dragged his tentacled arm away from the tray of human nourishment. He slithered out the research suite, seething in bitter angst at his shipmate.
The intergalactic zoology surveyor, Darwiz mused over the food items in front of him. An extensive journey through light years of black, empty space at the behest of His Majesty’s galactic zoological collection administrator, only to retrieve something so seemingly insignificant.
He sniffed at the rows of dark brown squares in one tray. They consisted of mostly covalently bonded simple sugars while the other tray held small crocks of sticky, light brown paste derived from an earthbound angiosperm, neither could satisfy an infant on their home world of Englen.
“Chuck-Lat and Pay-Nutt Batter…” Darwiz said to himself.
Captain Fitzrog rejoined him in the research suite, dragging along a young human male of breeding age. His ragged clothing hanging off his flesh, the famished human immediately caught the scent of the food paste and looked frantically around for the delectable nourishment.
“He senses the foods,” Darwiz observed. “Let him choose.”
Fitzrog pushed the human forward with his slimy tentacles and urged him to the tray of food. The human shuffled apprehensively toward the display of sustenance at the table next to the watchful scientist.
After a moment’s hesitation, the human dived head first into the food trays. He grabbed the little dark brown squares and shoved them into his mouth, then used his fingers to scoop out gobs of the paste, shoveling it into his packed mouth.
Darwiz scrawled some notes on a clipboard and watched in interest as the human finished off the food on the two trays. Looking disappointed at the end of his meal, the human frantically searched the room and quickly spotted excess trays of the food in the storage window on the adjacent wall. He lunged at the window with ferocity but was quickly subdued by the restraint collar on his neck.
Darwiz scowled at the human and said to the captain, “This one was starving. Get one that is well fed and see how he likes the morsels.”
Fitzrog, holding the remote control to the agony inflicting restraint collar, growled at the specimen. The human limped painfully out of the research suite followed by Fitzrog, who returned moments later with a plumper, livelier human, this one also a male.
Darwiz introduced this human to the trays in the usual manner. The human appeared interested immediately. After a moment’s reluctance the human picked up one of the squares and savagely chomped on it,the dark substance smeared on the corners of his mouth, oozing from his lips.
The plump human smiled and seized another square with zeal, this time dipping it into the paste. Savoring the mix, he chewed for a long time before indulging in a few more bites. Before long, both trays were bare. Again, Fitzrog led this human forcefully away before he could raid their stash of the human nourishment in the surplus window.
Fitzrog returned one last time to the research suite, this time unaccompanied. He noticed a contemplative gaze on Darwiz’s face, taking the expression as suspicious. Darwiz had a way of dragging out an expedition to include more sampling of some alien planet’s outlandish native fauna, delaying their return to Englen, an annoying prospect to the already naturally agitated personality of the alien captain.
“The humans derive much pleasure from the morsels,” Darwiz grumbled. “Even the fattened one seems to enjoy the scraps.”
“It’s a drug!” growled Fitzrog. “They are addicted. It’s obvious!”
“It’s not a drug, you idiot!” retorted Darwiz. He resumed his pontification sliding along the cold metal floor of the research suite. “The abominable mystery of it! The food items would hardly sustain the humans, yet they are eager to indulge, even the fattened one. It makes no sense.”
“It must be a drug!” was Fitzrog’s continued response. “Look at how they sense it when they walk into this chamber. It must have properties that they can sense.”
Slithering over to a new set of trays, Darwiz pulled out a jar of the paste and a tray of the brown squares. Squinting with all three of his eyes, he searched the food for an answer to the secret of the humans’ strong compulsion to the substances. Something flickered in his brain. Perhaps the strange anatomy of the human beings was to blame for this strange, anomalous behavior, this savoring of orally derived nutrition.
“Some primitive species still utilize microvilli in their oral orifices for sensory ingestion,” Darwiz spoke aloud.
“Disgusting!” reviled Fitzrog. “Such unevolved creatures, to taste with their mouths.”
“We could emulate the sensory stimulation in our own ingestion orifices,” said Darwiz. “It may shine some light on the abominable mystery.”
“Is it safe?” inquired Fitzrog.
“Nothing is safe when studying these filthy animals,” replied Darwiz. “We could get more samples and test more humans to be sure.”
“Not a chance!” shouted Fitzrog. “Let’s ingest the morsels.”
Darwiz dipped a brown square into some brown paste and popped it into his oral cavity. He snatched up another piece, scooped out some paste, and shoved it at Fitzrog who uneasily plopped it into his maw.
The glucose in the food immediately reacted ferociously with the tumultuously high oxygen content inside the aliens’ bodies. Chain reactions of combusting carbohydrates expanded the air inside Darwiz and Fitzrog, forcing their gullets to swell to an engorged state.
The aliens writhed and spun in agony as their midsections burst in a conflagration sending hot, purple goo and burning gases all over the research suite’s sterile steel floors as squares of chocolate and jars of peanut butter lay innocently on a germ-free tray, waiting to carry out that abominable mystery in the mouths of gratified humans.