"Here, let's start with some not too drastic changes so we can make sure everything works okay on a full human," you suggest. "I'm going to leave you mostly human for now."
"MOSTLY human?" he parroted curiously. "For NOW?"
You type C so you can input the changes but don't actually edit many of the settings. There are dozens of menus, each with dozens of sub-menus, but most of a subject's characteristics will auto-adjust to accommodate the least redundant choices. You're really proud of the convenient text-based interface you designed. If you only change the species setting, it will automatically calculate the most closely equivalent version of his new species so that you don't accidentally end up with (for example) a 72-kilogram mouse or a 28-year-old mayfly.
For now, you limit yourself to making one of the most minimal species changes possible.
SPECIES: H. SAPIENS NEANDERTHALENSIS
You press a keyboard shortcut to finalize the changes and enter the confirmation code. A progress bar shows up on the screen and a soft buzzing sound emanates from the old photo booth.
"Hey, um, I think it's happening. Something's starting to feel strange," said Jonas as he shifted uncomfortably in the booth. His bones were thickening up. He got a slight headache as his skull flattened, his chin reshaped, and his brow region grew out into a bony ridge. His nose broadened and his muscles bulked up.
"I'm feeling like a hulk!"
His body hair filled out and it was over. He was a stocky, hairy, muscular specimen of early man.
"Congratulations, Jonas. You're a real live neanderthal!"