Ty felt like it'd be really nice to be someone- anyone- else. At least for a bit. He'd retain control of his mind and body since the ovum he came from was the same, but the person who'd be born would be changed around by coming from a different sperm. And so he wished, "I wish I would keep full control of my body, but that a different sperm to the one I formed from would fertilize me."
After a long time going in reverse, time began to flow forwards again. In Ty's mind's eye, he saw two people, naked and eagerly preparing to fuck. Having never seen them before, and technically being part of their bodies, it was easy to put aside his knowledge of who these were and just focus on how arousing seeing two people fuck felt.
When Ty saw the man put his cock inside the woman, hold her down and start thrusting in and out of her, his arousal grew more and more intense. Their motions were tantalizing and restless, and Ty watched with great anticipation as their pleasure seemed to radiate through to him. At last the man came, shooting masses of cum inside the woman's pussy and then pulling out, his semen dripping from her.
Ty felt the sperm gradually approach him, and soon the tiny cells were swarmed around him, trying to break inside and wearing away the walls they found desperately. At last one broke through and it felt to Ty like something pushing inside him as it fertilized his egg form.
Now Ty wondered what the person he would be looked like...