There seems to be a large problem with engagements to Shampoo in self
insertion fics, (Also Ukyo/boy friend Thing but I won't go into that.) My
biggest problem with this is the Acidental KO thing. Shampoo's laws state that
she must be defeated in battle.  ...IN BATTLE... while I do understand the
joke value of this... problem Beating someone and accidentaly Knocking them
out are two different things. When Ranma beat Shampoo it was always in a
battle of some sort. Shampoo would not marry someone because they hit her the
head while turning around. Cologne would be the same way. such an act *could*
prompt Shampoo to challenge said person to save face or reputation. But
accidental knock out is a very weak probability. 
Gomen

Catbert.