This man was having trouble with his performance in bed. So he went to his local BlueCorp pharmacy and they recommended their new Panthera Performace Pills.
Derived from proteins in lion DNA, these pills allow you to go at it dozens of times in a single night!
Of course, the maximum dosage was one pill two hours before the event, taken no more than twice in any one week.

So when he got home from work, waiting in his bedroom for his wife, he decided to give her a nice surprise. Ignoring the recommended dose, he downed the whole bottle in one go.

Immmediately he could feel the effects. He felt strong, masculine, and incredibly horny. He felt like an animal. But his chest was really itchy...
Pulling open his shirt, he was shocked to see that he had grown a huge amount of chest hair - and he could see more growing at an impossible rate!
He growled in pain as something long and fleshy forced its way through his pants above his ass, and he instinctively moved to stand on his toes as his feet burst through his socks.

He grunted as his face morphed, becoming rugged and feline, and his hands mutated into wide, clawed paws. As he began to burst through his clothes, he had time only to look in shock at his hands - now paws, before falling on all fours, his body swelling and changing into that of a huge adult lion.

As his mind becomes fuzzy and his memories slip away, replaced by bestial instinct, his last human thoughts are
'Man, is my wife gonna be pissed...'