- And where are you planning to put that, exactly? - Vanessa asked, staring with half-terrified, half-excited look at the object in front of her.

- Wherever you want. - Ferb replied nonchalantly.

His restrained demeanour was what simultaneously drove Vanessa crazy, and made him even more attractive to her. To this day, she wasn't sure how come over the years she got interested in, befriended, and then fallen in love with the boy genius, who, despite being four years younger than her was a year above her at college. She often thought their relationship as a form of game, to find what could break the stoicism of her boyfriend, which very often translated to "how long will he last tonight".

However, something told Vanessa that this evening she will be the one to scream, especially as she examined the machine Ferb brought to their bedroom and placed next to their bed.

One part of it looked familiar; Vanessa owned a pair of vibrators, but this one, mounted on a longer metallic pole looked vaguely familiar, and she didn't have to look far for the inspiration of the shape. Vanessa leaned over the machine and gave the rubbery cock a soft kiss, throwing a sideways glance at her boyfriend.

- Okay, I guess sticking your cock in a pool of... uh, I don't know, ballistic gel, shouldn't count as cheating. - she spoke, stroking the replica of Ferb's cock.

- I used a condom. And when making molds, its the alginate that comes first. - he corrected her immediately.

- Well, we'll see about that...

Vanessa gave the rubbery cock another kiss and in one single move got rid of the black jacket covering her body. Ferb almost automatically gravitated towards her, ready to unhook her bra, but found himself facing her naked breasts and her already hard nipples. Momentarily hypnotised by the abundance of Vanessa in front of him, he flinched slightly when she fell onto her back, dragging her black leather leggings up, together with her panties. Ferb grabbed them and helped her take the last pieces of clothing that covered her body. A moment later, Vanessa arched one more time, exposing her chest and her already wet sex to her boyfriend towering over her.

- So... what are we gonna do with it? - she asked again, massaging her puffy lips, while Ferb disrobed himself equally fast.

- You decide.

Now that Ferb has gotten rid of his clothes, Vanessa took a good, long look at both phalluses, one natural and already in a state of full arousal, the other fake, but permanently hard, mounted to the machine. Though it looked stationary, the multitude of tubes and links on the machine's arm suggested that it could be as flexible and versatile as Ferb himself. Vanessa smiled, and jumped to all fours, waddling seductively towards Ferb.

- I'm not gonna pretend I didn't notice that this... - she pointed to the machine - ...is located just at the same height as this... - she closed her lips around his cock, giving it a quick kiss - Which makes it perfect for spitroasting me. In fact, I would even say that you set this machine up in such a way deliberately.

Ferb raised his brow.

- You are lucky that's exactly what I want...

She got on her knees, placing a soft kiss on Ferb's jaw

- I trust you completely, with this. - she whispered - Just tell me what to do.

- Enjoy it. - was his only answer.

A subtle, whirring noise reached Vanessa's ears, and she flinched when the tip of the artificial cock brushed her folds. She lost her balance enough to drop to her original position, facing Ferb's cock, while the fake one continued gently touching her opening. She waddled a step back, bracing herself for the machine's first intrusion. She let out a yelp when the cock parted her lips for the first time, and she used that moment to engulf Ferb's cock, partially to muffle her perverted, almost primal scream.

At once she pressed further back, letting the Ferb-like dildo fill her even more, though she was sure it could do that on its own. And sure enough, she heard more noises, and the angle the cock entered her has changed, brushing her clit next time, which would have filled their room with more moans, if her mouth wasn't occupied sucking on her boyfriend's real cock.

- It monitors the position... the position of your bum. - Ferb explained, keeping one hand on Vanessa's head, just like she liked.

Vanessa let out a soft murmur of approval, pushing Ferb's hips towards her, taking more of his length inside her. She was going to praise him, but her voice disappeared in the presence of dozens or so other moans her throat was generating, responding to the impossible to describe feeling of getting stuffed from both ends with two copies of the same cock. But it wasn't just the fact that two of her holes were being filled by the same man she loved. It was the *way* they all worked together.

Just like she would normally do, Vanessa bounced her hips back and forth, responding to the moves of her mechanical lover, so that its pushes would be as deep as possible. At the same time, whenever she retracted, so did Ferb, resulting in his cock reaching the very end of her mouth when they moved forward again.

The trio moved in this organised, immoral ballet for quite some time, building speed with each and every push. Vanessa noticed that as they continued fucking her, Ferb stepped, or rather waddled, a few inches forward, and as a result, he was now deep-throating her every time, while his electric-powered double brushed her clit with a copy of his balls, dangling back and forth with each time it filled her to the brim.

Like a well-oiled machine, the three fuelled each other passion, and in case of the machine, its neural network, controlling the tempo of the scotch yoke mechanism, learning and detecting changes in Vanessa's behaviour.

If Vanessa could face her boyfriend, and use her mouth, she'd send him a smile of deep satisfaction. Above her, she heard first, tiny moans and grunts coming from him, and by Ferb's standards, it was almost as if he was shouting the most perverted obscenities. The subtle change of his grip on the back of her head meant he was on the straight road to his climax, and so was Vanessa, her mind hazed by the indescribable feeling of being filled by seemingly two copies of her boyfriend.

A gentle pat on her back caught Vanessa's attention, forcing her to look up, at Ferb's face, stricken with unmistakable grimace of an oncoming orgasm. Before he was able to ask the question, she replied with a tiny nod, followed by a guttural "Mhm!", and let their bodies ride on their own.

- Va...Vanessa!

Her name, cried in his natural, deep voice was what pushed her to the edge. With her lips still closed around Ferb's cock, she let out a muffled cry, hoping her teeth wouldn't graze his delicate flesh. She has climaxed before while giving him head, and learned how to do it, but this time, she feared the pleasure was far greater. Her walls spasmed around the artificial cock, coating it with supple amount of her natural lubricant, which only seemed to speed up its moves.

As she was till riding on the wave of her climax, the synchronised moves of Ferb and his double suddenly changed; Ferb let out one more loud grunt, and in one move, he pushed himself deep into her at the same time as the machine, and did something that almost brought Vanessa to climax again.

In one moment, Vanessa was flooded with not one, but two streams of warmth, one filling her mouth, the other her pussy. While Ferb was coming in short pulses, supplying her with fresh amount of thick, musky seed to swallow, the machine did it in a near continuous fashion, pouring more and more liquid inside deepest parts of her sex. Neither her boyfriend nor his robot has ceased their moves; Ferb's hips still buckled every time he pulsed more cum for her to drink, and it seemed that he was able to replicate the same erratic, jittering motion with his machine, who occasionally pushed and pulled between its torrential gushes.

Ferb moved his hands to Vanessa's shoulders, at the very time her body gave up after being used not by one, but two copies of her lover. Ferb retracted his cock first, letting Vanessa take first, proper, long breath in quite a long time, and when her knees gave up, she slid from the fake cock onto the bedsheets. A moment later, she felt one last splash of warmth covering her backside, before Ferb turned it off.

Vanessa rolled to her back, still gasping for air, and not just because of the face-fuck she was being subjected to. The machine, still leaking its come, towered to her left, while Ferb was forced to succumb to the force of gravity as well and fell to the pillows on her right. She was glad to see a rare, goofy smile decorating his face, and responded to it with a smile of her own.

- Well, boys... you did a fantastic job. - Vanessa sighed, trying to lift herself up.

Only now she felt the uneasy feeling between her legs, and saw how virile the machine was: a small pool of white, sticky fluid, dripping from her well-used opening has formed on the bedsheets, and grew with each second, as more kept leaking from between Vanessa's lower lips, still contracting in an aftershocks of her climax.

- Ferb, I'm sure you'd be able to do it... But please, tell me I won't give birth to a cyborg, or something...

- That would be an android. - Ferb replied - And no, it's fake semen.

Reflexively, she dipped her fingers in the pool of cum, and brought it to her lips.

- Tastes just like you, though.

Rolling away from the mother of all wet spots, Vanessa waddled, swinging her hips in slightly less alluring fashion towards her boyfriend, letting her spent body slump over his. At once, Ferb's arm closed around her, resulting in a deep, lazy murmur of satisfaction escaping Vanessa's lips.

- How did you enjoy the experiment?

- Complete success. - she replied, placing a soft kiss on his chest.

- Of course we will need to repeat it to verify the data...

- Oh, yes, we will... - she let out a languorous moan, caressing his chest even more.

- And we will need to test the remaining five of six possible combinations.

Ferb expected to hear another moan from her, but instead Vanessa rose to her knees, towering over her with her arms crossed.

- Six? I think someone got their math wrong, Ferb. Did you count handjobs, or boobjobs? - she pressed her breasts against each other, and then his face - And double penetration? What about that? Let's face it, we can do so much more with this machine... Oh, and I didn't even thought about turning it into a strap-on! And, can you make more than one?

Once she stopped counting, Vanessa smiled triumphantly, staring at her boyfriend from above. Ferb's widened eyes expressed not fear, but excitement known only to inventors who have just discovered a whole new realm of uses for their designs. And Vanessa would be more than willing to assist him in exploring it.