My son was a HUGE pirate fan at the same age.  He even took a "pirate class" at the park district.  There he was introduced to Backbeard (Backbeard and the Birthday Suit &amp; Backbeard:  Pirate for Hire).  Seriously funny books; it took a lot of will power to read those to him without breaking into fits laughter (every time!).

I'm going to have to look into the 2 potty humor contributions, he's 6 now so the potty humor is still going strong and his little sister seems to enjoy it as well seeing as her favorite song now is "Twinkle Twinkle Little Butt" and her favorite book is "Everybody Poops".  :)