Heh, pulling the Spongebob argument is below the belt.
Okay, so I was raised by parents who let me believe in Santa Claus (And yeah, I was devastated to find out. Bias revealed. Nothing to see here, move along). However, had I expressed a fervent belief in the existence of Lion-O or Optimus Prime, I like to think they would have corrected me. I'm not sure how to put this into words, but what I'm getting at is that while characters like Spongebob are culturally iconic on a scale similar to that of Santa Claus, there is a difference. I'm not sure if the difference is based on longevity, close relationship to a major holiday or life event, or something else entirely. So in my mind we're comparing apples and oranges.
But I do agree that it is *possible* to expose a child to the truth without causing (much) harm, and your experience is evidence of that. I guess what I don't understand is why a parent would think that way. "Oh it's okay to let them think that now, I'll break it to them easy one day". Well, what if you fuck that up? I'd rather tell the truth from the start than have to fess up to a lie later on. It still boils down to whether a person should lie to the people that trust them most in the world. And I think the answer to that should always be "no".