You enjoy cuddling in the bath with your mermaid girlfriend. Out of curiosity you reach up and feel her tailfin. It feels like regular skin, just like the rest of her tail. You marvel that your wish has taken on such an unexpected form, but you feel happy that your girlfriend is not so trapped by the wish as it had first seemed.
Your legs are starting to feel funny and you assume it's just from sitting in the bath a bit awkwardly. As much as you'd like to spend more time in the tub, you better get out and stretch your legs.
"Sorry to cut things short" you say to Amy, "but I need to get out of the tub."
Amy gives a teasing pouty face, then pushes herself up with her arms and pulls her tail under her to shift from her tail being behind her back to a seated position at the opposite end of the tub with her tail in front of her. "You can get out first then lift me out."
You try get up and out of the tub, but your legs are weak and you can't stand up. You try several times, but it's more than just your legs falling asleep.
Amy looks concerned. "Are you okay?"
"No, something's wrong with my legs." A moment later your legs spasm. What's going on?! "Is this some side effect of my wish?" you wonder aloud.
"I thought you said the genie only allowed you to change one person?" asked Amy.
"That's what he told me."
"What was the exact wording of your wish?"
You try to concentrate on what you said to the genie rather than the feeling of your legs being the consistency of jelly. "'I wish that my girlfriend would be permanently transformed into the mythical creature of her dreams, but that the transformation would not negatively impact our relationship or our love.'"
Amy thought for a moment then blushed. "I have an idea what's happening. It has to do with your wording - the mythical creature of my dreams."
"But you turned into a mermaid like you always dreamed."
"I didn't just fantasize about being a mermaid; I fantasized about being a particular kind of mermaid..."