"Heh, heh, looking pretty good in red rubber," you say admiring your reflection, "Thanks, Santa."
"Oh, you haven't seen anything yet! Hohoho," says Santa.
"Huh?" you say feeling your nipples tingle. As you watch your reflection your right pectoral shifts and expands. Your right shoulder and arm also swell up. Your eyes widen as you see that your entire right side from your neck to your ankle has swelled up with muscle stretching the tight fitting rubber suit. "Whoa?"
Your eyes focus on your unchanged left side. Your hand feels the pert muscled right pec and then feels the nipple of your unchanged left pec. As your index finger and thumb pinch your nipple, your hand is jerked an inch or two to the left. Your left pec swells, your shoulder, leg and arm also inflate into muscular counterparts to your beefy right side. Now your eyes focus on your six pack abs, and on the larger bulge at your crotch. Even your feet are bigger. You grin.
"Fucking cool, Santa! Any more surprises?" you ask turning to look over your shoulder at the reflection of your back side. The rubber disappears into the your muscle-surrounded butt crack. You can see your back and shoulder muscles, and glutes and thigh and calf muscles all clearly outlined through the taut red rubber suit.
"Oh, yes, but I don't think you'll like it as much as you do the muscles," Santa says stepping toward you.
"Oh?" you ask rubbing your itchy chin.
You laugh as you see the beard growing from your chin and the moustache on your lip. "Oh, facial hair growth? I like, but you're right I like the muscles more. Say, am I hairy all over?"
Santa grins broadly and hands you a gold chalice. "Some Christmas Spirit to fill your body with the warmth of the Season?" he asks.
"Sure, cheers, Santa!" you tips back the cup and drains it.
You look at Santa and blink, "Whew! That was sweet, and potent. What's in it?" he asks with a belch.
Santa looks away for a moment. He asks in a soft voice, "Have you ever wondered how I've stayed alive for all these centuries?"
"Never really thought about it. But I guess, you're immortal right?" you say.
Santa turns around and gives a hearty laugh. "Well, in a way, I guess. I am the Christmas Spirit," he says.
You look at the empty goblet in your hand, "You mean like in this cup?"
"Exactly!"
"Huh? I--" you suddenly feel disoriented. Your arm moves of its own accord, or at least not of your accord. You put the goblet back into Santa's sack, and begin to collect your box and ribbon and stow them along with the baby powder cannister inside the sack. You don't know why, it's as if your body is a puppet, and you're not pulling the strings.
Everything seems to get blurry. You close your eyes, suddenly you feel weaker, and your hand brushes against your bloated belly. You can feel that you're not clad in latex any more. You clear your throat, "Say, Santa, what the-"you reach for your throat. The voice coming from your mouth is the voice of the old Santa.
"Mwahohoho!" you hear your own voice say. You see your now heavily muscled body flex as it easily tosses Santa's bag over his shoulder. "Well, you were a naughty boy, and you wondered how I lived all these centuries. Well, now you know!" He put his finger against his nose, and adds, "You know the box creates the Santa suit according to your inner desires. This is the first time it's been rubber. It feels good." He nods and vanishes from in front of the fireplace.
You are alone in the room.
You walk over to mirror as if in a dream. It has to be a nightmare, right? You tug at your old white beard. It's real. Your vision is blurred and dull, as cataracts cloud your eyes. You open your red velvet coat to reveal a white hairy chest. You grin, at least you've got chest hair. You yawn and climb back into bed to complete your long winter's nap.