public with sharing class ExtensionController{  
public ApexPages.StandardController standardCon;    
public ExtensionController(ApexPages.StandardController con){  
standardCon = con;  
}    
public void populateRelAccFields(){  
Opportunity opp = (Opportunity) standardCon.getRecord();  
opp.Account = [select Phone, Type from Account where id =: opp.AccountId];  
} 
}