A potato

The idea came almost entirely out of the blue, and its absurdity almost made him cackle. But it should be possible, right?

Ducking back into the kitchen, Aaron grabbed a lumpy root vegetable and tried out the blue tweezers. Sure enough, a sluggish, green wisp came free as he pulled, hanging limp by its tail. Placing that one in another container, Aaron took the potato and the jar containing his sister's soul back to the sitting room to watch the effect take place.

Emily even glanced at him from where she sat on the floor as he entered.

"What's that? Is that jar glowing? Why are you holding a potato?"

Aaron shrugged. "Science."

"Whatever," Emily said, turning back to the screen.

What Emily was ignorant of, her soul seemed terrifyingly aware of. It crawled into the lowest corners of the jar's rim as Aaron lowered the potato inside, pressing itself against the glass yet unable to escape being sucked into the flesh of the tuber. As the last of the glow vanished into the potato, Emily's body slumped forward onto the carpet.

Resisting the urge to laugh madly at what he'd just seen, Aaron instead put the jar down and went to check on his sister's body. It was still breathing, but its eyes were fixed on an empty point in space, every limb completely slack. Without her soul, Emily had become a vegetable.

Wait a minute.

His heart racing with anticipation, Aaron darted back into the kitchen and retrieved the potato's... soul? He'd never have believed they could have one, and to be fair the limp, green thing didn't seem to be especially spiritual. Even so, he carefully up-ended the jar over Emily's inert body.

The spirit slid out like a lump of jam, jiggling as it hit Emily's skin before slowly sinking into her flesh. For the longest time, nothing happened, but after several uncertain seconds she turned her head ever so slowly towards Aaron and looked at him.

Aaron waited.

'Emily' blinked.

And that was about it. Aaron now had a potato for a sister and a sister trapped in a potato.

A tiny bink noise made him turn around. The potato was gently rocking in its jar, occasionally making contact with the glass as it tried to escape. Aaron had to suppress another mad laugh as he watched it. On another impulse, he filled the jar with water and screwed the lid on, watching the floating vegetable banging itself against the sides of its prison.

It didn't seem especially thrilled.

Still, Aaron thought to himself. Mission accomplished. No way she'll be interrupting any of my shenanigans tonight.

He had to stop himself there. Forcing your sister to swap bodies with a potato was almost definitely already shenanigans.

Aaron shrugged. It was a good start.