Can the Marauder's Map be deceived?

[Briony Coote]

No: HPFGUIDX 54178

I have three questions about the Marauder's Map:
 
1 - Why didn't Peter Pettigrew show on the Map during the years that the
Weasley twins used it, or when Harry started using it?
 
2- In GoF, why did Barty Crouch Jnr show as "Barty Crouch" and not
"Barty Crouch Jnr"?
 
3 - Why did Barty Crouch suddenly disappear off the map when he was
right there in Snape's office, disguised as Moody?

"Briony"


[Non-text portions of this message have been removed]