Magna Doodle says "Nice Nails Chandler!"
In the uncut DVD version of the episode, it is revealed that Monica has also knocked a hole in the ceiling. Monica asks their neighbor under them, Mrs Katrakis, if she had met Kenny, who lives above them.
When Rachel walks in on Monica after she's carved all the holes in the wall, Monica is reading a book called "Like a Hole in the Head" by Jen Banbury.