My sister wants this cake for her baby shower next month, sorry I can't give credit to the artist as I'm not sure where she found the photo. How do you stack a cake like this? There's no dowel through the bowl, how do you keep this thing stable???

There are certainly scads of dowels in the two tiers under the fishbowl.

This cake would be driven to the party site in two sections.

Then the fishbowl only needs a solid acrylic plate under it and over it to be stable.  That's one reason for the generous piped borders on it.

http://www.obseussed.com/2012/02/dr-seuss-baby-shower-party.html

The cake was made by Amanda Groom, in the UK. I believe this is she:

http://apieceofcake.uk.com/

That doesn't show the cake, but you could e-mail her and ask her how she did it.