On Sat, 2 May 1998, Greg Phillips wrote:

Okay...  Here's my latest idea.  Anyone care to take a stab at it?

Ranma is sick and tired of Shampoo chasing him, trying to drug him, etc.,
so he decides to take matters into his own hands.  He offhandedly remarks
to Shampoo that Mousse has gotten a lot better lately and could easily beat
her anytime he chose, but simply refused to do so because he didn't want to
hurt her.  Shampoo, her pride wounded, says that Mousse could never beat
her no matter how hard he tried.  Ranma bets her that Mousse can beat her
and that if he does that she will leave Ranma alone.  Shampoo asks what she
gets if Mousse loses and Ranma agrees to go on a date with her.  Ranma
challenges Mousse to a fight, then during the fight, he (where Mousse can
see) dons a long purple wig and starts taunting Mousse in Shampoo-ese
("Stupid Mousse!  You no can win!  Give up!")  Then, Ranma runs off,
allowing Mousse to keep him in sight the entire time.  Then, Ranma bolts
into the Nakohanten with Mousse close behind and hides.  Mousse enters and
screams for Ranma to show himself.  Shampoo emerges from the kitchen,
demanding to know what Mousse is doing.  Mousse, mistakes her for Ranma in
disguise and beats the tar our of her.  Ranma shows up, congratulates the
now stunned Mousse, then leaves.

This has already been done in Donny Cheng's fic entitled Ranma and
Shampoo, where he tricks Ryoga into fighting Shampoo by doing almost
exactly as you describe, except for a few plot differences.

http://www.geocities.com/Tokyo/Ginza/4537/

Of course, there's also my opinion that Mousse couldn't beat Shampoo if
she was a cat, but don't let that discourage you...

-Natsume Ranma Ranma
-------
The sardines weren't worth the trouble.  A few more shots, then 
Ryoga-san would overheat and explode.  Ducking around a corner, 
I managed to lose him as I entered the ramshackle residence of 
my Anime supplier.

One look at his face and I knew that I was betrayed.  "Tell me."
I insisted.  He refused, so I slammed him against the wall.
"Last chance.  Where can Ranma-Ranma find good fanfics?"
"Try Jason Liao." he whispered, before he slumped to the floor.
I heard the sounds of a door splintering as I left through the 
window, one step ahead of Tendo Heavy Industries...