By reprogramming his brain!

"You did give him the strong sedative, right?" Dr Bluder asked her lackey.

"Y-Yes Ma'am! He won't wake up for about ten hours..."

"Good, move him into the VR chamber..."

The lackey made good on his Mistress's order and wheeled the gurney into a darkened room, Dr Bluder told the lackey to leave her as she began Ultraboy's 'treatment'. She'd already programmed a montage of clips of her and also of women being inseminated, while also having her voice going through his ears as she seductively whispered how he should be willing to not only have sex with her, but also to breed her.

While he was having his brain re-wired, Dr Bluder moved on with the next part of her plan, going over to a special cupboard, she pulled out two syringes. The first one she injected into herself, it contained a permanent fertility booster, the strongest she could make (legally or illegally) while the second one she injected into Ultraboy's balls, it contained a **** that would keep his testicles full of super-potent sperm.

She then went back to the cupboard and grabbed a pump and one final syringe, she injected this one into Ultraboy's groin and quickly attached the pump to his cock. The syringe contained a **** that would add two inches to his cock, taking it to 10" long, but it also made his cock thicker, using the pump she could size his cock to fit her pussy so that when he came inside of her, none of his spunk would leak out.