does spongebob have brain?

Yes, he does. And it looks like a normal human brain (or just a normal brain, really). There was an episode where Plankton made a controlling mechanism and attached it to Spongebob's brain in order to get the secret formula of the Krabby Patties. It was literally attached to his brain, so we get to see Spongebob's cranium. Also, Spongebob decided to see what was up with his unnatural motions and decided to peek inside his own mind. Literally. His eyeballs rolled over until it was seeing into his own head. Such fun.

Yes spongebob does have a brain and it looks like a normal one not a sponge. There are a couple episodes where they show his brain.

I would say that SpongeBob definitely has a brain and it is a normal sized brain with normal functions,and there has been several episodes where we have seen SpongeBob's brain like the episode where Mr Krabs wanted spongebob to give him a penny,and SpongeBob's brain fell out and got it to get back in his head,and the one where Plankton was using a device to control SpongeBob's brain,and even the one where SpongeBob had Patrick shape him into a ghost and his brain was showing.

In an episode, I ever seen his brain. It looks like human brain.