This was actually a Final Jeopardy question on one of the kid Jeopardies about a year ago. The question was something like "who is the only female character in the Pooh cartoons?" (not worded exactly right, but you get the idea). The answer was Kanga (which I got right and my husband did not!), so therefore Piglet must be a boy!
Male of course. Christopher Robin (the real one as well as the fictional one!) was a boy, so all his toys were boys, except Kanga, who was stuck being Roo's mom and therefore didn't qualify to be a boy
Contrariwise, a couple of my daughters' baby dolls are sometimes boys, but not many of them and not for very long. Steve The Baby, for example, has only been a boy for a few weeks, and his name just got changed to Newspaper, although I am told he remains a boy for now.
This question pops up on the DIS pretty regularly. I remember one thread on the old Debate Board about Piglet's sex which was absolutely hilarious. I so wish we could still bring it up and read it.