The puzzle packet contained two copies of this puzzle. The first trick was to notice that this was not an error, and that the two copies were not quite identical. There were various clues to this: the title is ``Twins,'' suggesting the twinning of the puzzle was not an accident; the blurbs talk about twins whose lives were nearly identical, suggesting these twins are nearly but not quite identical; and the blurbs themselves are nearly but not quite identical.
Once you realize this, it's clear the puzzle is one of those ``find the differences'' puzzles where you figure out the ways in which the pictures differ.
You should find the following nine differences:
The final step is to convert these differences into a final answer. If you extend the grid lines by drawing horizontal and vertical lines through the drawing, you will notice that each of the differences lies within a single ``square'' of the grid. The column and row headings for each difference can be combined to form a letter and an offset, e.g., Y +13. This can be converted to a letter by indexing into the alphabet. For example, Y +13 gives L because if you go 13 letters past Y in the alphabet (wrapping around the end of the alphabet if necessary), you reach the letter L.
The differences yield the following leters:
|Vertical robe line||Q+10||A|
The resulting letters, when anagrammed, form the answer, GRAPHICAL. This adjective can mean either ``formed by drawing'' or ``appearing on a coordinate grid'', both of which describe the puzzle.