Old Shame: One book has several early strips that Pastis made when Pearls was still a webcomic. He derided most of them for being Out of Character.
There are also various strips that were Not Ready for Primetime and those Pastis thought were either too weird or just plain sucked, and ended up getting scrapped.
Recycled Script: Averted for the most part, but a pair of strips really stand out: September 29, 2011, a daily strip, was recycled less than a week later into October 02, 2011, a Sunday strip, with an extra punchline from Rat. This was pointed out in some of the latter strip's Gocomics comments.
Thesestrips as well, which ran about a month apart in 2008.