Peter Parker, known more famously as Spider-Man, was clearing things up in the apartment he shared with his model/actress wife, Mary Jane Watson. He often did housework because, well, her job was a lot more demanding than freelance photography. He often lamented how busy she could be, wishing he could do something about lightening the load. He might've actually found a way to do that...
He hears the door swing, MJ comes through and gives him a kiss. "How was your day?", Asks Peter. MJ lets out a groan, "Photoshoots are good money, but they're exhausting too!" MJ plops down on the couch, kicking off her shoes, "And I've got ANOTHER one tomorrow... Whoever said being pretty is easy is full of it."
Peter decides this is as good a time as any for his proposition. "Well..." He said, "What if you didn't have to go? What if... Someone could fill in for you?" MJ looked up at her husband, confused, "I hope your not talking about clones. You don't have particularly good experiences with them, in case you forgot." Peter shook his head, "Nuh uh, clones never end well. I have a way to fill in for you!"
MJ looks at him again, "Somehow I doubt anyone would confuse you in a red wig and a dress fives sizes too small for me." Peter wags a finger, "Oh ye, of little faith! Check this out." Peter gets out a leather belt, lined with a bunch of glass phials with a green liquid. "Chameleon stepped up his disguise game, the stuff in here can temporarily change his DNA for a few hours. At least, it would if I hadn't confiscated it from him..."
MJ gets up from the couch, walking over to Peter and inspecting the belt, "How does it work?" "First, you need some DNA from the subject", says Peter, who plucks a hair from his wife's head. She gives him a sour look as he takes out one of the phials, unscrews the metallic top, and drops the hair in. The liquid reacts, bubbling and hissing as the hair dissolves. The liquid continues to bubble like a carbonated drink, Peter lifts it up like a toast. MJ's eyes widen, "Pete, are you sure that's a good-" But Peter gulped down the serum, shaking his head from the taste, "Very... medicinal..."
Peter shakes his head again, then clutches his stomach, "Stuff works fast!" Gurgling issues from his stomach, but Peter suddenly reaches for his chest with his other hand. Something was going on with his right pectoral, it was expanding in his hand and was soon followed by the other. He was growing breasts! Peter was sweating now, his hair was slowly growing longer and changing color from brown to red. Suddenly Pete's face soured, he reaches for his privates as he felt the changes going on downstairs. His hair was down to his shoulders now, an pooled around his face. He jumped and yipped as his body became an exact replica of his wife's. Eventually, Peter was still, taking her new hands to brush all of the hair out of her face to show that her face was exactly like MJ's too.
MJ gasped at the sight of her husband, now an exact duplicate of her in every way. Peter gave an embarrassed but cute grin, "See? It works." Peter tries to walk back over, struggling due to the weight on his chest. MJ walks over instead in mercy, holding Peter in her arms and feeling their breasts being pressed together. "Pete, why'd you do this to yourself?"
The innocence in Peter's eyes was strangely adorable to MJ (remembering they were also her eyes) "Because...I love you. And I want you to have some time to relax." MJ could still see some of Peter in those eyes, and she kissed him passionately. Peter felt the rush of female arousal, different parts of her body lighting up in ways totally alien to her.
They break the kiss, looking each other in the eye.