My parents bought Thomas the Tank Engine things for my little brother when we were small. Books, toys, and maybe also movies (I know we saw him on TV - thanks, Sky card). But I loved Thomas more than my brother ever did, and I would take all of the books into my room to read. I was definitely very into Thomas trains (I remember that Percy was my favorite because he was smallest), and trains in general (The Railway Children was my favorite book, and I coveted my brother's electric train set).
Funny thing, though, I've heard the Thomas theme recur a lot in conjunction with autistic children. I wonder what would cause him to appeal to them especially?