[Answer]-Foreign Key Relations between 2 apps and User model

But this isn’t “extending the user model” at all. You have a reference to a completely different model, via a ForeignKey. I don’t know why you’d expect favorite_color to suddenly become an attribute on the User model.

Instead of a ForeignKey (which implies many ExtendedUsers for each User), use a OneToOneField. Then you can follow the relationship directly:

user = User.objects.get(pk=1)
print user.extendeduser.favorite_color