I'm sure Teddy didn't think that Superman was a real guy. What he probably meant is, Superman looks like he's made of flesh and bone and lives on the planet earth (according to the comics), whereas Mighty Mouse is a drawn cartoon that lives in ficticious Duckburg. It's a typical kids statement that wasn't thought through for even a second. Like most of what Teddy does and says ("I cherish these moments")
Oh and by the way what the
hell
is Goofy?
Books are a uniquely portable magic.
~Stephen King