It'd started innocently enough - the used bookstore was on the same block as the pet store, so it wasn't much of a hassle to take him along with her - and getting his book had gone easily enough once he'd stopped fawning over the owner for ordering a first edition The Man who Fell to Earth for him, something he didn't stop babbling on about until they got to the fish section - he'd managed to keep his luminous fish alive for nearly a year, anyway - and the trouble only came when Penny said she wanted to buy some Siamese Fighting Fish. Which, for Sheldon, was a remarkable testament to his growing strength of character.
"Why this kind of fish?"
"Because I can have a pet if it can live in five gallons of water or less, and these are prettier than the goldfish."
"But Penny, you can't buy Siamese fighting fish."
She glared at the aquarium shaped like a giant frog. "Then how come they sell them here?"
"It's obviously a mistake on their part. Siam hasn't existed since Thailand changed its name for the second time in nineteen-forty-nine. Calling these 'Siamese fighting fish' is a misnomer of tremendous proportions, especially when you should be calling them Bettas."
Penny took a deep breath. "So how come they call Siamese cats 'Siamese'?"
He huffed. "That's an associated breed name accepted by various cat breeding organizations as a way to distinguish certain individuals by a specified set of physical characteristics, fur coloration, and temperament."
"And it doesn't have anything to do with where they're actually from."
"Of course not."
She nodded, and said slowly, like she was talking to her five-year-old nephew, "So calling the fish Siamese..."
"...Oh." He blinked several times. "Oh!" Penny held back a smile. He nodded, "I see. In that case, you want to buy the blue one."
"Why the blue one?"
"It's the same color as Luke Skywalker's lightsaber, pre-Special Edition."
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