I started reading Calvin and Hobbes when I was about 5 or 6. It was a short while after the comic ended, and I became addicted to it, buying and reading every book in the series within the next few years.
Maybe I was just a dumb kid, but when I was young it never actually occurred to me that Hobbes was just Calvin's imagination. I always assumed he could either switch back and forth between plush and real tiger to disguise himself or it was the Santa effect where you couldn't talk to him unless you knew he was a real tiger.
In my kid mind, I'd watched a lot of TV shows and movies where weirder stuff happened, and to me there wasn't any reason why Hobbes couldn't be a magical stuffed tiger who could come to life. I even remember believing some of the imagination storylines to be true, like the ones where Calvin clones himself.
When I was younger, Calvin and Hobbes was about the very real magical adventures a kid and his pet tiger went through.
