Erik knew what was happening to him even as he started gaining muscle mass.
Quickly he started stripping off all of his clothes but although, unlike his brother Nate's change via Lunar Ecstasy, this was totally unplanned, he relished it none the less.
Erik watched in fascination as his finger and toe nails lengthened while his hands and feet started taking on a more animalistic shape.
A fire grew in his groin as his penis gained more girth and size before becoming encased within a sheath, but even that failed to keep the new organ completely hidden from view.
Erik couldn't help pawing (no pun intended) his new cock even as fur began to spread all over his body.
He felt his facial features start to change even as the discomfort in his rear indicated a tail was sprouting from his ass.
It was a race of pleasures as the final alterations to what was once an ordinary human male were completed and now a wild, lusty animal stood even as Erik experienced the first orgasm of his new life.
His parents were getting ready for bed when they heard it.
A loud and triumphant roar coming from somewhere within their house!
"Nate?" the father asked, thinking their other son might have returned.
"No. That wasn't a wolf howl," said the mother, before both realized what it was.
"ERIK!" they screamed, racing out of their bedroom and down the hall to their son's.
In their haste to check on him they didn't bother to knock as they entered, but thankfully Erik hadn't bothered to lock the door.
Both were aghast to see the sight before them.
Instead of their son a much taller weretiger occupied the room.
The anthropomorphic being was about to climb out of the bedroom window he had just opened, but paused to look at them.
"Sorry about the mess," he growled in a new, much deeper voice than the one he had before.
His parents looked and saw a very large quantity of a creamy white liquid scattered across the room's otherwise clean carpeting.
"Erik?" his father asked, wondering how this happened.
"That Lunar Ecstasy is great stuff!" their son exclaimed. "This happened just from handling Nate's leftovers. Imagine if I had gotten a full dose!" said the weretiger, flexing one now muscular, furry arm.
"Where are you going?" his mother asked.
"I'm really horny and need to mate," Erik replied lustfully, even as his folks noticed the hard tiger penis protruding out of his new sheath.
"B-but... you're still a virgin, aren't you?" his mother asked, even as she felt the blush of embarrassment color her cheeks.
"Hopefully not for much longer," Erik said. "Don't wait up!" he added, leaping out the window, his tail swishing happily as he disappeared into the night.