It would surprise many the types of documents that have
been approved by the Courts as being valid Wills.
Wills don't necessarily need to have an official (and legal)
look about them but they do need to be in writing, signed by the
testator and witnessed by two people.
We see situations where that hasn't occurred. It might be
that someone has tried to amend their Will by writing changes on
the Will itself, or has tried to write or type out a new Will.
Sometimes a document is located where it's not immediately
clear if it was even intended to be a Will (eg. it doesn't
state that it is a Will, it hasn't been signed and witnessed
properly, it has pages missing, etc).
Often those types of documents won't have any legal effect.
However, the Court can sometimes approve them
as a valid Will (an 'Informal Will'), depending on the
circumstances.