After contemplating their options, Jerry piped up "How about more than two arms? Say...four arms altogether?"
"You mean the 'tetrabrachius' option?" a surprised Josh asked quizzically.
"Well...yeah." Jerry answered back. "Or some variation thereof."
"Ah, you mean like brothers Giacomo and Giovanni Battista Tocci." the program wizard interjected.
"Who?" both heads quizzically asked in unison.
"Ah...that never gets old." the program wizard replied bemusedly. "I'll bring up their photo."
An image appeared on the screen of two conjoined twin boys in the nude, their torsos clearly joined in a Y-shaped configuration. Each boy had their own head and matched set of arms, but both clearly shared a navel, a pair of legs, and a set of male genitals.
"Definitely NOT like that, Wizard." Josh exclaimed, seeing how limited such a configuration was for their purposes.
"Agreed." said Jerry. "Other than being able to put your arm behind the other twin's shoulders, that form is extremely limited."
"Very well." the program wizard replied. "What did you have in mind?"
"To be honest," Jerry answered, "...I was thinking something more along the lines of a two-headed person with four arms, yes, but with both of the left arms being on the left side and controlled by the left head..."
"And both of the right arms being on the right and controlled by the right head?" Josh quizzically interjected, beginning to see his twin's train of thought.
"Well...yeah." said Jerry to Josh. "Essentially, instead of each of us getting a matching pair of arms, I'd get both right arms, and you'd get both left arms."
"I get it." replied Josh. "But...where would the extra arms connect to our body?"
"I was thinking somewhere on the sides of our torso," Jerry explained. "You know, like...underneath our existing arms."
"You mean...like an insect?" Josh asked.
"Possibly..." Jerry replied.
"No offense, bro," said Josh, "...but first off, last time I checked, nothing outside the insect kingdom has more than four limbs - well, five, if you include a prehensile tail."
"Except in in the worlds of comics." Jerry calmly retorted. "But I see your point."
"And secondly," Josh continued, "...if we ever want to have these and any other 'extras', future or otherwise, on a more permanent basis, we should focus on finding a way to have their presence make sense."
"Not that I don't get what you're saying," Jerry quizzically replied. "...but I'm not quite sure I'm following you."
"Consider your idea of having your proposed extra arms underneath our existing ones." Josh elaborated. "Even if they were indeed fully-functional and we were the ones controlling them, doctors looking at us might think they're the remnants of an undeveloped triplet..."
"And decide to remove them on the spot...even without consulting Mom and Dad first?" a floored Jerry nervously asked.
"Exactly." Josh finished. "And we'd be dealing with 'phantom limb' for the rest of our lives...or at least, our entire childhood. But what if the extra arms were attached in such a way that doctors couldn't remove them without extensive - AND expensive - reconstructive surgery?"
"Not to interrupt, gentlemen, but I believe I may have a solution." the program wizard chimed in. "That is...if you'll both indulge me."
"Sure." Jerry replied.
An image appeared on the screen, showing the two boys from above. The image then cut to an outline of their heads and shared shoulders, a set of crosshairs appearing dead center in the median between their heads. As the boys watched intently, the outline gradually shifted, revealing two sets of shoulders forming an 'X' along the axial plane with the crosshairs as a pivot - Jeremy's in red, Joshua's in green, both with their respective owners' heads off center. The two sets of shoulders scissored back until the shoulder furthest from one head was directly behind the shoulder closest to the other head: in effect, the two new shoulder joints appeared directly behind the existing joints.
"Whoa...that's an interesting setup there." Jerry quietly exclaimed.
"What do you know...'Great minds think alike', indeed." Josh interjected. "But in all seriousness, that's kinda what I was going for. Since the shoulders would be placed with one pair in front of the other, doctors will have tried figuring out how to remove the extra pair, but there'd be a catch: the rear arms would be too far back on their own and the shoulders wouldn't connect to our collarbones, and the front arms wouldn't even have shoulder blades."
"And since surgery wasn't as advanced then, they couldn't really have done anything..." Jerry added, his eyes widening upon fully realizing the implications of what the Chronivac wizard was proposing. "Also...it looks like our heads would move forward slightly as a result of the change, which might take care of our unwanted extra nipple."
"Precisely." the program wizard chimed in. "Care to try it out?"
"I'm willing to give it a shot." Josh replied before turning to his twin. "And you, bro?"
"I'm in." Jerry nodded. "But we'd still control only the limbs on our respective sides of our shared body, right?"
"Of course." the program wizard replied. "For it to work, though, I'll need the two of you to sit up straight in your chair, with your respective arms hanging off to the sides. Once you're both ready, we'll begin."
After taking a few moments to get themselves into position, both heads turned to the computer and said in unison "Ready."
"Very well, gentlemen." the program wizard replied. "Commencing upper limb and shoulder replication now."
Both felt their respective arms go both limp and numb within moments of giving the go-ahead. It was happening: their arms and shoulders were multiplying. Though neither twin felt any pain, they could clearly see and feel them stretching, becoming so thick they couldn't bend their fingers, even if they wanted to. A second hand was emerging from the originals. A crease appeared in each twin's arm and shoulder, running down both sides and dividing them vertically: it was clear an entirely new arm and shoulder was starting to separate itself from each of the originals. After a couple of minutes, both twins could make out the details of their new limbs. The crease deepened to the point that both sets of arms and shoulders were just barely connected by a thin layer of skin, the crease itself stopping just short of each twin's neck. Then, the new pair of arms and shoulders divided completely and took position directly behind the original, the divide between the front and rear shoulders running from just short of each twin's neck to between the front and rear armpits on each side.
As soon as the procedure was complete, both twins took stock of their new limbs and found they had no trouble controlling them. It was just as easy to move and manipulate their new arms and hands as the original: they could even raise and lower their front and rear shoulders independently of one another.
"Whoa..." Jerry quietly mused while raising and lowering his front and rear arms and shoulders in rapid succession, giving the illusion of flapping them like a dragonfly's wing. "This is SO trippy..."
"If those were actual dragonfly wings, it would be." Josh replied. "But the way you were flapping your arms, the best you'd manage right now would be a hover."
"Hehe...you got a point there." Jerry sheepishly replied back, running his front hand through his hair while his rear hand and forearm rested on the arm of the chair. "All the same, I'd say our new arms turned out great. What are your thoughts?"
"Likewise." said Josh, holding his front hand to his face in thought as he tried feeling inside the crease between his front and rear shoulders with his rear hand. "Not really sure how we'd ever manage to wash in these areas, but...other than that, I've got no complaints."
"And if this is what it's like for us to have four arms," Jerry began musing while looking at his fully-outstretched arms side by side, his eyes widening as his mind began racing with possibilities. "...just imagine if we had six! Or even eight! Or maybe even..."
"Don't even think about it, bro." Josh answered back, holding his front hand up as if to stop Jerry in his tracks. "I think having two arms each is enough for us right now. Anything beyond that is...just plain overkill."
"I'm inclined to agree." the program wizard interjected. "My analysis indicates that without further augmentation of your motor cortices, the presence of any additional limbs beyond this point may tax your minds to the breaking point, possibly rendering you both borderline sub-sapient. Don't forget, Jeremy, that you and your brother Joshua are co-controlling a shared body."
"Fair enough." Jerry sighed, dejected by having one of his - and Josh's - shared fantasies shot down by a biological technicality.
Looking down at his and Josh's shared chest, Jerry could only grumble at the sight of their third nipple, its mere existence seemingly taunting them.
"So..." Josh nervously chimed in, hoping to both change the subject and lift his twin's spirits, "...what do you want to do next?"