He rubbed her breasts as he thrust into her with all his strength, feeling the incredible pussy of the alien suck his cock even deeper in. Its abs flexed with each twist of its hips, squeezing his cock in ways he’d never imagined possible. He was hitting against the creatures womb, and its body was shaking with anticipation, its thighs gripping him hard from either side. He could feel its body tensing, ready for an orgasm, and as its pussy clenched onto his cock one final time, he let his cum shoot out inside of her.
With a cry of pure sexual gratification, the alien came, accepting Carl’s cum deep inside its body. Its body arced back, dragging his cock further inside it as it leaned back, pulling the last bit of cum out of him. It slipped off his cock and swung its head back forward without a moments hesitation, breasts swaying and ass jiggling as its lips wrapped around Carl’s still-hard cock.
The scientist let out a small cry of surprise, but after the first few sucks he was more than happy to let the alien continue. He could feel the tip of his cock being sucked down the alien’s throat, feel the creatures tongue caressing his girth and feel the suction, as strong as the vacuum of space, working his shaft. He watched the alien shake its hips as it sucked, felt its breasts squeeze against his legs and balls, and then let another load flow.
The alien drank, sucking down mouthfuls of cum. Carl watched its throat work as it swallowed his seed, and if he hadn’t already been spent, he was sure he’d have gone hard again. The alien's tongue wrapped around his cock, licking and scraping off every last drop of cum, and then it sat back on its feet, fat thighs squishing against its calves as it licked its teeth clean and savored the last of his cum.
Then, to Carl’s surprise, it spoke.
“I fucking needed that. Who knew a lab boy’s cock could be that big and delicious?” The alien leaned forward and pressed its breasts against Carl’s chest, then ran a finger along the line of his jaw. The light shifted as it did so, illuminating the inside of its head which he now realized was slightly transparent, and he found himself looking through it into a pair of human eyes. “So. How can I help you get ready for round two, lover?”