Baking a cake in a bowl. What should the bowl be made of?

Yes, using a bowl will affect cooking times. To make shapes like that, generally cakes are made in layers, filling between layers, and then sculpted to shape, then iced or fondant is used. I wouldn't recommend using bowls. OR, just shell out the money and get the mold you already know exists. If it's important, it will be worth it. Trying to figure out cooking times, type of bowl (would have to be oven proof), etc. would be almost impossible. FYI: No all Pyrex products are oven proof. You'd have to be sure... it should be on the bottom... even of clear gl. If it isn't there, it's not made for use in the oven.