Spongebob Squarepants is a cartoon on Nickeloden loved by most children and hated by most parents.  However, with that said it is a cartoon and of course the stuff that goes on in that cartoon is pure fiction.  So with that said Spongebob can live in a pineapple under the sea if he wants no matter what the mathematical world says.  

One of the things I learned in college (besides my Social Security Number) was the term suspension of disbelief.

Definition: a willingness to suspend one's critical faculties and believe the unbelievable; sacrifice of realism and logic for the sake of enjoyment. dictionary.com

That is exactly what Spongebob is, enjoyment for children no matter how annoying it can get.

So this mathematician needs to read that definition and move on.  Spongebob's pants are squarish, Gary's shell is, Gary's shell and Spongebob does indeed live in a pineapple.