Slowly Jeff's cock began to push outwards, both in girth and length as he watched. He held his hand over his cock, feeling his tool growing into his waiting grip. The pleasure was intense, he could feel every pulse of growth as if it were someone stroking his shaft expertly.
As his cock grew to normal size he began to stroke it, bringing waves of pleasure washing over him. He gripped his shaft and began to work it as it grew. It was extending mostly in length now, bulking up a little with each pulse but pushing from his groin at a much faster pace.
Suddenly as he rubbed himself he felt his cock twitch. He was starting to gain control over it as it grew longer. He relaxed his grip and began to work his cock under its own control, starting with small twitches but building his control as he moved it. He found he could control it much like a snake, twisting and writhing totally under his control even when aroused (which he was). As it grew longer and more powerful he could feel his control over it increasing.
Slowly the pulsing in his crotch dimmed as he neared the end of the transformation. His cock was nearly three feet long now, and nearly four inches across. It felt extremely powerful and muscular, like a python, and every touch caused him a wave of arousal.
Jeff snaked his new cock around his arm, flexing it and feeling it tighten powerfully around his arm. He was surprised at how strong it was, he had barely flexed it at all and he could already feel the ciculation in his arm cut off.
Jeff smiled wickely, his cock unfurling from his arm and snaking around in front of him like a tentacle, totally under his control. Now he just had to find somewhere tight and warm to stick it....