My dad has worked at Nickelodeon for my entire life, and once when I was a kid I happened to be at the studio at the right time and was invited to take part in the theme song for a new show, Spongebob Squarepants. I was about 8 at the time (now 21) and I had no idea what the show was. I thought the concept of a sponge for a main character was ridiculous.
My Dad also directed Hey Arnold and has animated for Family Guy, Rugrats, The Simpsons, Spongebob, and the Fairly Odd Parents. I asked him to do an AMA, still waiting on it! As for me, I have also worked as a movie extra and intern for Nickelodeon, so feel free to ask about that, too.
I don't really have proof, but here is my dad's spongebob wiki page: http://spongebob.wikia.com/wiki/Tuck_Tucker
And this is me with my dad: http://i.imgur.com/iAeQd2o.jpg