Pettigrew, the Twins, and the Map(new thought)

[Risti]

No: HPFGUIDX 45094

All this talk about Pettigrew and the map has got me thinking.

I've always wondered just how the twins figured out how to use the 
map.  I mean, the words "I solemnly swear I am up to no good" 
couldn't have just come out of their mouth by chance, could they have?
(although I've seen some very good FF's where they have).  What if 
Scabbers/Pettigrew showed them how discreetly?  Maybe there's a code 
word that brings up a page of 'instructions', and late one night 
while everyone in the dorm room was asleep, he transfigured himself, 
muttered the words, then quietly transfigured himself again.  Maybe 
he even set an old charm in place that allows only fellow marauders 
to see each other on the map, figuring that was a very unlikely 
event, and knowing he needed to hide his identity from the twins.  Or 
maybe my mind is just working over overtime.

~Risti