Variation 3 by ImoutoCommissions

   Though Pikachu, in human form, is rather short, Togepi is even 
shorter than he is. She comes only
   to chest height, with spikey, platinum blonde hair, and skin just as 
pale. Her egg shell takes the
   form of a one piece swimsuit, white with the same red and blue 
pattern on the outside.

   "It'th so great to thee you, big brother!" she lisps, giving Pikachu 
a hug. "And Mama and Papa
   too!" When she addresses Ash and Misty as such, the two are very 
visibly flustered, which
   amuses Brock to no end.

   When the group gets back to their journey, Togepi insists on riding 
piggyback with her "big
   brother", something that Pikachu is all too happy to comply with. 
He's delighted to spend time
   with her like this, and it's nice to be able to bond outside of their 
Pokemon forms, which are a lot
   closer in size.

   However, when they start camping for the night, things get a little 
awkward as Togepi insists on
   sharing a tent with her big brother, something that Ash isn't too 
sure of, but she gets so passionate
   about it that Pikachu eventually convinces him to share his tent with 
Brock so that she can get
   what she wants. He and his little sister sleep in separate sleeping 
bags that night, sharing their tent
   completely innocently...at least at first.

   But in the middle of the night, Pikachu is woken up by Togepi nudging 
him as she climbs into his
   sleeping bag, and when he groggily asks her what she's doing, she 
says, "I had a bad dream, big
   brother! Can I thleep with you?" 

"Of course," he replies, unable to 
turn her down, but he quickly finds himself regretting his decision. As 
she wriggles around to get inside and get comfortable, she rubs up 
against him, or, more particularly, her butt does. This causes his cock 
to grow stiff against his will, and he hopes that she doesn't notice, 
squirming uncomfortably to pull back, since there's so little fabric 
between the two of them.

But then Togepi reaches back to touch him, asking, "What's that?"

He jumps up suddenly at her touch, and when she turns to him, and sees 
him sitting there with his obvious erection, she innocently asks him, 
"Do you want to mate with me?" Pikachu is stunned into silence, but 
Togepi takes this reaction as approval, and pulls her swimsuit to the 
side so that she can sink down onto him.

Togepi lets out a soft gasp of pain as Pikachu pops her cherry, but she 
decides to wait out that pain and holds her breath for a moment, until 
she's able to relax and take it completely. Meanwhile, the warm 
tightness of his little sister around him leaves Pikachu too overwhelmed 
to properly respond as she grows used to having him inside of her.

It isn't until she's relaxed more and begun to bounce on his lap, 
resting her hands on either of his shoulders, that he's finally about to 
regain his composure and say something to her.

"This is wrong!" he shouts out. "We can't do something like this, you're 
too young and I'm like a brother to you and...and..."

"But how can it be wrong if it feels so good?" asks Togepi, rather 
naively.

He tries his best to resist the pleasure he feels and to resist the urge 
to thrust up into her, the urge to spill his seed inside of her and the 
urge to let his electricity run wild, but it just takes one more look at 
her face contorted with pleasure to completely shatter his resolve.

He says a silent prayer to Mew that Misty won't find out about this and 
skin him alive for it before he leans up to kiss Togepi, and flips them 
so that he's on top of her, his instinct taking over. He begins 
thrusting hard into her, pounding her into the ground beneath her and 
leaving her a moaning mess. However, he's the one who loses his control 
more quickly, as once he's given into his desires, he has no hope of 
slowing himself down anymore.

There is no thought of trying to hold back or slow down, and he reaches 
his orgasm all too quickly with a scream of pleasure that matches his 
native tongue. Togepi cries out with delight as a pleasant burst of 
electricity surges through her and as his seed fills her, and she only 
lasts a few moments longer herself.

"I'm tho happy!" she cries out, "I've never been happier!" But as her 
pussy begins to clench around him with her orgasm, she begins to glow, 
and before his eyes, she changes form, evolving in front of him. Even 
the shape of her pussy changes around him as she grows, and when the 
glow fades, he can see just how she looks now.

Physically, she's about as mature as Misty with her body, and her hair 
and skin have turned snow white. The bathing suit she wore before has 
vanished completely, and instead, the markings that were once on it are 
instead all over her body, resembling tattoos. "Thank you for giving me 
such a wonderful experience," she says, her voice sounding a little more 
mature and her lisp gone now. "Hmm, maybe I should call you my little 
brother now, since I'm taller than you?"

"I don't know about that," he mumbles, a little embarrassed.

"Well? Are you up for another round?" Naturally, he is.

~X~

The next morning, the two of them have returned to their natural states, 
though now, Togepi is a Togetic. That is how their humans find them, 
curled up together, and they marvel at the change Togepi underwent.

But then Ash says, "Hey, what's that they've got there?" It's then that 
the three of them notice the object between the two Pokemon- an egg that 
looks just like the one that Togepi first hatched from.

Though they won't be able to get clear answers from the two Pokemon when 
they wake up, it isn't too hard for them to figure out what exactly went 
down between the two of them.