Ai am attempting to do a siting 3d spongebob cake for a child organization. I will be putting dowels in the cake as well. Is there any advice for transporting the cake so it won't fall?

I don't know the dimensions of your cake, but you might be able to use a flange screwed into your board (center it in the middle of the cake) and put some pvc pipe up through the middle (cut a hole through your cake layers and cardboards) and stack with dowels. That will give you added stability.

AThanks for your response. The cake is going to be two 9x13 sheet cakes cut in half, with cake boards between the levels. I was thinking about taking the top part off "where the sponge part stops and the white part of his pants start" and have it reconnected at the venue.

You will transport it complete.  I responded to your PM and will send you pics and instructions when I get your email address.