Nerves
Because half ghost anatomy sounds like lots of fun and I have way too much time on my hands. For those who don't know- a reflex, scientifically speaking, is a movement you have no conscious control over whatsoever. Catching a ball quickly isn't reflexes, it's reaction time. A reflex is when the doctor hits your knee and your leg jerks. It's a survival mechanism that has to do with the placement of nerves.
"Tucker you need to stop."
His only response was another poke on the top of his foot and giggles.
"Tucker."
Another poke, more laughter.
"Tucker I will kill your PDA."
Tucker's laughter quickly stopped and he narrowed his eyes at Danny.
"You wouldn't"
"Keep poking me and I just might."
Tucker smirked and sat on his hands.
"Well, at least we know now. I mean, it's good to know these things. Test your reflexes and stuff."
Danny glared at Tucker before rolling his eyes. The experience behind the discovery of his "ghost nerves" was embarrassing and unpleasant.
"Watch your foot, dude!" Tucker warned as he dropped his heavy backpack on Danny's foot.
Almost instantly, Danny's legs had disappeared and melted into a tail.
"Why are you-? You're in human form."
Danny just floated there, his tail flicking from side to side over the blue carpet of his bedroom, with a very confused expression on his face.
"I didn't- I don't-"
"Danny?"
"I have to concentrate on getting a tail in human form."
"...And?"
Danny looked up at Tucker, a grim look on his face.
"I didn't concentrate."
"Are you sure? Maybe you're just getting better at it."
"Yeah, but it feels tingly. Like when you hit your funny bone."
"Doesn't it normally feel that way?"
"No."
"Want to try again?"
"...Yeah."
Tucker picked up his backpack from the floor with a grunt and positioned it over Danny's foot again. He looked into Danny's eyes and the both nodded. Tucker dropped his backpack again and Danny's legs once again melted together into a smooth tail.
They looked at Danny's tail, then back up at each other.
"I don't know, man. Maybe it's a reflex. Want to take off your sock so we can check?"
Danny looked at Tucker with an unsure expression before he shrugged and took off his sock.
Tucker squatted over Danny's foot and poked a bunch of parts of it. He wasn't poking very gently either. Danny would probably bruise in the future.
Tucker kept prodding different areas of Danny's foot until he hit something on the very top of Danny's foot very hard.
Danny jolted and his tail smacked Tucker in the face.
"Ow, dude, did you have to do that?"
"You were the one trying to get my tail out."
"Because you let me!"
"Because you dropped your backpack on my foot."
Danny's tail snapped back and forth underneath him playfully. Tucker, not wanting to mess with Danny at the moment, decided to ignore the jab.
"It looks like we've discovered a ghost reflex."
Danny frowned at Tucker's seriousness before nodding.
"Ye-"
Tucker stepped on his newly reformed foot, causing it to fade back into a tail. Tucker smirked with an evil glint in his eyes.
"Tucker…."
"Yes, Danny?"
"Bye!"
Danny quickly regained his legs and sprinted out of his room, Tucker chasing after him with a cruel grin.
Whenever Tucker caught up with Danny, he stepped on his foot again, making Danny's feet disappear in a sensation of numb tingling.
Tucker eventually told Sam.
Danny never had legs when the three were alone from that day on.