As a Mum and as most mums will agree.... small children become obsessed with a subject. They will do nothing but hunt down stink bugs for months on end; or snails, or rocks! Every damn rock they find but every rock is fascinating to them. Then all of a sudden they couldnt give a darn about rocks and they are obsessed with dinosaurs.
Small children DO obsess with their bodily functions because WE stand there and clap and cheer and dance around them for quite a length of time in their short little lives during the time of "potty/toilet training".
I think I have also said it before that I know about some of these things because as my youngest is intellectually challenged there are very specific markers in development about when they do this and how long it lasts, etc. Parents of "regular" kids dont even think about it as thier children move on and reach different developmental markers, and they go ohhh and ahh over those. Its not like every intellectually challenged child stops at "poo". Its just one of 100's of markers that go to gauging where in a child's development they are falling behind, or arresting that that serve to assist in diagnosing just WHAT the problem is; and then how to best treat it.
On a clinical point of view: if you are a Special Needs teacher with 10 kids with different syndromes you also need to know these conditions and markers so that you dont leave little Johnny alone long enough to express his artistic bent with Sally and his poo.
who might just be that little girl who has a morbid fear of poo.
Kids obsessions with ONE subject or theme for lengthy times is also at the heart of modern marketing. After a large part of our household budget fed the beast that was "Dora The Explorer" (clothes, duvet covers, posters, cards, toys), one weekend they disappeared and Justin Beiber was proudly plastered onto every blu-tackable surface.
As she is the third child I had gained enough wisdom NOT to actually PAINT the current theme in PAINT on the walls like I did for the first child when she went through the "I love everything associated with the sea and under the sea" which was entrenched in every waking moment for two years...... and suddenly disappeared as the paint was drying on the last little mermaid I painted in the 12 foot mural on her wall !!!
Dont read too much into the whole poo thing. It MAY have been a plot line.... or TP may have been reminded of something someone had mentioned over dinner about someones little boy who was fascinated with it at the time. Parents do that. The kids move on, the conversation moves on but a brilliant author uses it as a sub-plot line years later.
OH! And Dotsie....... those guys? Perfectly normal. The tests show that while GIRLS move on from fart jokes and laughing at poo, boobs, willies and such like... apparently boys never do.... its considered perfectly normal and is expected.