You know, now that I think of it, I've been wondering for a 
while how the alternate Ryoga got engaged to Nabiki in "Ryoga 
Crossover."  And I've got an idea for how it started:

Ranma is wet, bruised and female, sitting totally dejected
on a grassy knoll.  Nabiki walks by, stops, looks at him
with curiosity but no great concern.

Nabiki:  What happened this time?  

Ranma:  I was in a fight with Ryoga.  Winning too.  Then we
both got hit by some water and I found out he has the same
curse I do.

Nabiki (smirking as she smells Ryoga's blood):  You mean...?

Ranma:  Yeah.  Akane's best friend, the one she trusts more 
than anyone, Ryoga's sister, Yoiko, is really Ryoga's cursed
form.  No wonder he knows everything that happens between
us and she always seems to say something to set Akane off 
against me.  Who woulda thought he was that sneaky?

Nabiki:  So why not tell Akane?

Ranma:  I tried.  You see, she showed up while I was beating
Ryoga, and naturally assumed I was beating up her best friend.
Which I guess I was, the two-faced scum.  Then both of them
beat me up together.  Akane won't listen to me, and tells me
that she'd never be engaged to a guy who beats up her best
friend for no reason and then tells lies about her.  I guess
Ryoga wins.  

Nabiki for the first time looks concerned.  If Akane is serious
this time, Nabiki might end up stuck with Ranma and all the hassles
that come with him.

Nabiki:  Oh come on, where's that never give up Saotome spirit?

Ranma:  Akane believes everything Yoiko tells her about me.  As
long as Ryoga wants Akane, I don't have a hope of getting Akane
to forgive me...  
	Wait, what if I was to get another girl for
Ryoga?  Ryoga's a really lonely guy, he might go for it since
Akane likes Yoiko a lot more than she likes Ryoga.  Ahhh, I'd
never find a girl crazy enough to go for Ryoga.  Heck, I bet
even you couldn't find a girl that nuts.

Nabiki gets a gleam in her eye:  How much?

Shift to:  Nabiki blackmailing Ryoga
           Ryoga going out with Ukyo
           Ryoga going out with Kodachi
           Ryoga going out with Asuza