As a boy, I loved the Disney movie-length cartoons of the Hundred Acre Wood and from time to time I still enjoy reading The Complete Tales and Poems of Winnie the Pooh by A. A. Milne. If you haven't read them, you should; there's a great deal of wisdom contained in them.
At any rate, after seeing the t-shirt the old theme song for the cartoons instantly found its way to the front of my brain. If you hear humming or singing, "...but most of all there's Winnie the Pooh. Winnie the Pooh...," now you'll know why.
And just so I'm not the only one singing it throughout the day: